Indian Journ al of Radio & Space Phys ics Vol. 3 1, December 2002, pp. 337-348

Space weather research in India: An overview

G S Lakhina & S Alex Indi an Instilllte of Geo magneti sm, Colaba. Mumbai 400005

Received 2 August 2002; accepted 27 Septelllber 2002

The regime o f space wea ther inc ludes the sun , solar wind . interp lanetary space, mag netosphere, ionosphere and the thermosphere . The immediate manifestations of space weat her events are the result o f solar n ares and corona l mass ejec ti ons (CM Es) lead ing 10 the occurrence or geomagnetic storms and substorms, appearance o f auroral forms, ionospheric di slllrbances, e tc. The so lar-terrestri al environment has a wide range of effects on many aspects o f our everyday li fe. Thi s paper di scusses var io us aspects o f space weather and presents an overview of the space weather research act iviti es in Indi a. T here is a need fo r a co mprehensive space wea ther prediction programme for Indi a in view o f the fact that the space- based syste ms are already being ex ploited for a variety o f applicati ons such as remote sensing and meteoro logy, radi o co mmunica tio ns. broadcasting, earth resources survey. e tc.

1 Introduction

In broad terms, space weather refers to the disturbed conditions in the near-earth ' s space environment due to the changes or events taking place in the sun . The primary source of space weather is the explosive events on the sun . Space weather sparks off on the surface of the sun , which is the major source of electromagnetic and particle energy and it can produce tremendous impact on the near-earth space environment. Sunspots are often associated with violent activity on the sun . They , thus form a major tool in pred icting the space weather di sturbances .

The sun emits electromagnetic radiati ons in broad spectrum of wavelength s, from the short wavelength hi gh energy X-rays and ultra-violet (U Y) emiss ion to visible light, infrared and solar radio emi ssion . Space environment of the earth responds within eight minutes to the changing nature of these primary solar emi ss ions. The short wavelength radi ati ons from the sun , like X-rays, UY and ex treme ultra-violet (EUY), ,ontze the neutral constituents tn the upper atmosphere of the earth , forming an ioni zed atmosphere ca lled the ionosphere.

In addition to electromagnetic radiati on, the sun emits continuously a stream of charged particles ca lled solar wind . The solar wind is a tenuous and hi ghly conducting gas consisting mainly of electrons and protons with a little bit of alpha particles and other heavier ions. At the earth's orbit, the solar wind has density of about 5 particles cm-" and speeds of -400 km s-' . Both density and velociti es are variable,

and the speeds can exceed 1500 km S- I during hi gh­speed streams. The solar magneti c fi eld embedded in the corona is dragged out by the constantly ex panding and highly conducting solar wind, thus fo rmi ng the interplanetary magnetic field . Solar wind interaction with the geomagnetic field gives ri se to the earth 's magnetosphere (Fig. I). Magnetopause boundary separates the plasma and fields connected to the geospace and the interplanetary medium. The magnetopause boundary layer is the site where energy

Fig. I- Schematic 3-dimensional view o f the earth ' s magnetosphere formed by the interaction of so lar wind with the geomagnetic fi e ld [Small arrows indicate the d irec tion of the magnetic fie ld lines. Thick arrows show the direc tion of e lec tric currents. Vari ous current systems present in the magnetosphere are shown. I

338 IND IAN J RADIO & SPACE PHYS, DECEMB ER 2002

and momentum is exchanged between the so lar wind plasma and the magnetospheric plasma. This energy is di ss ipated by several complex current systems arIsing due to the solar wind-magnetosphere interac ti on. When the energy accumul ated in the cross-tail current is released sudden ly in the form of hot plasma jets, it gi ves ri se to the phenomenon of substorm. During substorms, a large fracti on of the energy released from the magnetotail gets deposited in the hi gh lat itude ionosphere where it exc ites the auro ra. The form ul ation, characteri stics of the deposit ion and release processes of the energized plasma into the au roral regions cause va rious space weather phenomena. Thus, the solar wi nd acts as an agent for es tab li shing the sun -earth plasma co nnect ion .

Periodica lly the sun becomes hi ghly eruptive. Solar flare event is a mi ghti es t erupti on from the tenuous atmosphere of the sun , and it occurs predominantl y

, ..... .. ~ ~ -t ...... ' J.;; -;, -.. <,,;<~~, . .. . . , . . ~ -- .... , ....

... . .... . , .;:: .. ,.. ; .. • • ~ ..... < - .~ .... '"

during peri ods of large-scale changes in the sun ' s magnetic fi eld. The frequency of occurrence of solar flares becomes high during the high so lar act ivity cycle or solar maximum. The intense radiation from the so lar flare travels to the earth in eight minutes and their effects are visible in the magnetic fie ld records from the ground observat ions. Often, foll owing the ex plosion in the su n's surface, there is an erupti on of a cloud of electri fied magnetic gas from th e corona, called coronal Illass ejec ti on (CME), and almost 10 million tons of pl asma travelling at speeds ex tending up to 2000 km S- I is hurl ed into the interpl anetary space (Fig. 2). There is often a magnetic cloud l wi thin the CME. Magnetic clouds that are geoeffecti ve have a southward and then north ward (or vice versa) magnetic fi eld direc tional vari ation, When thi s magnetic cloud has a very hi gh velocity, it compresses the plasma ahead of it and forms a colli sionl ess shock. Behind thi s shock is a sheath

...,..~..! ... ,- ..: r to .. ", .. " . ..... .. .... .... ,-;, .. , ....

';' . ..... ,1" ,

.; ... .:.~ .1>,. ' :/' .... _ • •• • ~,,," •• , . . .. ' J I,""'" I •

~~~~:. ..... . ; .. .. , ,..~.)' ..

Fi g. 2- Whitc li ght image of so lar coro na during a coronal mass ejecti on (CME) on 23 Nov. 200 I. at 00 18 hI's UT. from thc Large Angle SpcClJ"Omclri c Coronagraph (LASCO) in strument on the So lar Heliospheric Observatory (SOHO) space craft ISolaI' fl arc and CME eman ate a huge amou nt or energy: III/age C(Jurlesl': "SOHOI LASCO (ESAI NIISA) " I

LAKHI NA & ALEX: SPACE WEATHER RESEA RCH IN INDI A 339

wh ich conta i ns heated plasma and compressed magnetic fields. These intense sheath magneti c fi elds can also cau e magnetic storms. The internal structure of an interpl anetary coronal mass ejecti on (I CME) is shown schematicall y in Fig.3. I f both the sheath fi eld and the cloud fi eld (i f present) have the proper ori entation, double storm s can result2

. In complex cases, where there are multipl e solar fl arings, there will be multi ple shocks and multiple pl asma and fi eld compress ions, and thus tripl e storms, etc. will result. Tsurutan i el al .3 demonstrated that the storm generati on mechani sm can be identi fied by examining the profile of the magneti c storm using ground magneti c field data. As far as the space weather effects are concerned, solar fl ares and coronal mass ejec ti ons, associated with large energeti c particle events and major shockwave di sturbances in the solar wind , are the two main causes that can give ri se to geomagnetic storms, intense auroral acti vity and other space weather related di sturbances in the earth 's near space.

2 Geoeffectiveness All solar fl ares and CMEs may not give ri se to any

big magnetic storm. The capability to cause big

SHEATH (ehocked .Iow eol., wind)

ri g. 1-Schelllatics of an interplaneta ry coronal mass ejection (ICME) IThe outerillost part is denoted as the ICME/ci ri ver gas. The inner part is the magnetic cloud. As the speed of the ejecta is Ill uc h hi gher th an the back ground so lar wind. a shock is fo rilled ahead of an ICM E as shown here. The sheath reg ion contains the shocked slow so lar wi nd plasma and compressed Illag netie fields. (taken from Tsurutani el at6 )J

magnetic storms depends on several fac tors. The most important is the trajectory of the solar fl are/CME ejecta. Obviously those solar fl ares/CM Es that do not hit the magnetosphere could not give ri se to any di sturbance or geomagnetic activity. The geoeffec­tiveness of the ejecta, as far as the capability to cause geomagnetic storms is concerned, depends upon the structure of the magnetic field and the shock waves associated with the ejecta. It has been well establi shed that the primary cause of magnetic storms is intense long-duration southward interplanetary magneti c fie ld (IMF) which interconnects the earth 's magnetic fie ld and allows solar wind energy transfer into the earth's magnetosphere4

• Therefore, depending on the orientation of the magnetic fi elds carried by the CME cloud, earth directed ejections could produce big magnetic storms by dumping a large amount of solar wind energy into the magnetosphere mainly by the process in volving magnetic reconnection. The interplanetary (lP) shocks compress the magneto­sphere and could cause instantaneous spurt in the magnetopause current, leading to abrupt increase in the horizontal component of the magnetic fie ld recorded on the ground magnetometers. This stage of the storm, known as the ini tial phase, may persist fro m 0 to 16 h. Recent developments on the inves ti gations on storm dynamics attribute the solar antecedents of intense storms to coronal mass ejections during solar max imum5

.6

. Whereas in the descending phase of the solar cycle, the high speed streams emanating from coronal holes can cause recurrent geomagnetic storms at 27 -day interval7

Following the shock wave, the main phase of the storm sets in, during which average global feature of a magneti c storm is the unm istakable reduction in the hori zontal intensity of the terres tri al magneti c field lasting for a few hours to days . This decrease in intensity of the hori zontal component of the magneti c field is due to the increased population of energeti c charged particles, whi ch make their entry by the injection fro m the near-earth magnetotail into the inner magnetosphere. SingerS suggested that the gradient dri ft of the energeti c particle trapped in the geomagnetic fi eld carri es a westward fl owing ring current encircling the earth in the equatorial pl ane. During magnetic storms a large amount of energy is di ssipated in the polar regions, leading to profound changes in the global morphology of the upper atmosphere. An example of the solar fl are/CME, causing a big geomagneti c storm, is shown in Fig. 4.

340 INDIAN J RADIO & SPACE PHYS, DECEMBER 2002

40400 nT '!"sfe

40300 Tirunelveli 'H'

40200

40100

40000

39900

39800

00 UT hrs

Fig. +--Mag netogram fro m Tirunelve li Magneti c Observatory showing the geo mJgnetic storm CJuscd by a solar fl are/CME [The cffect of a powerful X- class solar fl are th at occ urred on 10 Apr. 2001 , Jt Jbout 0525 hrs UT modified the ionospheric currCIll and affected the magneti c fi eld within J fcw minutes as shown. The CME erupti on follow ing the fl are led to an intense shock as observed by the ACE spacecraft on II 'h April at 1520 hrs UT, after almost 34 h. The impact of the shock on the magnetosphere is seen as a suddcn impulse on the magnetic rccord at around 1545 hrs UT. Subsequentl y, the development of the intcnse main phase assoc iated wi th thc wcstward ring current is cv idenLI

Coinciding with the decrease in the field, a magnetic storm is general ly accompanied by intense auroral bri ghtening. Occas ionall y the auroral ovals expand equatorward with the occurrence of auroral substorms or magnetospheric substorms. M cPherron<J, Rostoker el a/. III and Iyemori and Rao ll defined the phenomenon as a transient process initiated on the nightside or the earth resulting in the energy transfer mechani sm between auroral ionosphere and magneto­sphere in these expanded ovals. Severe magnetic storms are relati ve ly rarefi

. However, during magnetic storms intense substorms are observed in the polar regions and subsequent development of intense ionospheric currents II. Apparentl y, perturbati ons of so lar ori gin fo rm an important link in the complex chai n of so lar-terres trial relati ons. A flow chart showing Ihe chain of so lar-terrestri al processes that are involved in causing magnetic storms is shown in Fig. S.

II is believed that most of the thermospheric dens ity perturbations are transported from high lati tude po lar reg ion, whi ch is affec ted most due to the energy dumped in thi s region, to low latitudes. Thi s transport is affec ted by trave lling ionospheric disturbances (TIDs) and large-scale wind circulation. These perturbations take significant time (more than 3 h) in propagating from polar to low latitude region and may affect communication severely. Recent

observations have shown that energy and momentum do not fl ow only in one direction , i. e. from solar wi nd to the magnetosphere, but there are also important fl ows in the opposite direction, i .e. from magneto­sphere to the interplanetary space as well. A n important recent discovery by Dagli sl2 concluded the dominance o f oxygen ions in the energeti cs of the storm time ring current. It is a puzzle how the oxygen ions are ex tracted from the ionosphere, energi zed to few hundreds keY energies and then injected into the ring current. Recent results from Imager for Magneto­pause to Aurora Global Explorati on (IMAGE) have shown that ex traction of oxygen ions takes place almost instantaneously in response to the inter­planetary disturbances, giving ri se to magneti c storm . Some observations have pointed out the inadequacy of D'l index as a reliabl e indicator of the kinetic energy content of the ring current, and questioned the use of thi s index as proxy for the perturbation fi eld.

3 Effects of geomagnetic storms on technology

(i) Solar erupti ons direc ted towards the earth are potentially harmful to advanced technology. Advancement in technology has taken effecti ve turning points i n th e comrnun ication link, navigation and space-borne satellite systemsl .l.I" .

Modern instruments and links around the globe are increasingly dependent on elec tri ci ty and

LA KHI NA & ALEX: SPACE WEATHER RESEARCH IN INDI A 34 1

Electromagnetic radiation

Sudden Ionospheric Disturbance

Solar Flare

SUN

Particle radiation

Solar Wind

Impact on Earth's Magnetopause / Magnetospheric compression &

tremendous energy input

Flare effect on Magnetic records

Geomagnetic storms recorded at Magnetic Observatories

Fig . 5--Flow chart representing schematica ll y the chain o f solar-terrestri al processes giv ing ri se to space weather di sturba nce~ in the near-earth 's space env ironment

electroni cs. Technological systems in space and on the earth 's surface are subject to adverse effects fro m geo magneti c di sturbances IS. Duri ng such events, the magnetospheri c compress ion by the solar wind forces the magnetospheric boundary inward past the geostationary satellite pos ition (Fig.6).

(ii) Geosy nchronous Communicati on Satellites orbiting the earth arc many in number. A largc geomagneti c storm can enh ance the number of electrons and ions hitting these satellites, leading to intense spacecraft charging, whi ch would cause damage to the spacecraft.

(iii ) Enhanced levels of solar radiati on associated with intense flare ac ti vity on the sun can also cause heating and expansion of the neutral atmosphere and increase the amount of atmospheri c drag that a satellite ex peri ences in an unpred ictable manner.

(iv) Auroral acti vity and intense substorm di sturbances cause dropouts and changes in path s of HF communication and increased sc intillation degradation of radi o signa ls at high frequencies, and disrupt surveill ance tracking of the satell i teo

(v) The di sturbance also induces ex tra cu rrents in the wires of the elcctrical power grid. producing temporary overload. Such severe geomagneti c di sturbances can induce DC currents in power lines and can cause destruction of power sta ti on transformers.

(vi ) Geomagneti call y induced currents and voltages can also damage long pipelines and communi­cati on cables. These currents affec t the conductors Ll sed fo r telecommunication.

(v ii ) Very hi gh energy (- I MeV) charged part ic le flu xes released during storms and subs torms

342 INDIAN J RADIO & SPACE PHYS, DECEMBER 2002

Fi g. ()-Space wea ther cl'fects on the tec hnological systelll s, ranging rrolll di sru ption in sate ll ite cOlll llluni cation to the destru cti on in power lines and underground cable IReprinted, with a sli ght Illodirication. with the permi ssion rrolll L. J. Lan zerolli. Bell Laboraturi es. Lucent T ccililolog ies. /

pose a serious radiation hea lth hazard ror as tronauts.

The erkcts or geomagnetic ac ti vi ty on techno­logical systems are becoming crucial as components arc miniaturized with advanced elec tronic components. Increased demands of appropriate descript ions and accurate predictions of geomagnetic disturbances are becoming a crucial fac tor in the modern advanced technology sys tem.

.t Geomagnetic field measUI-ements and space weather

Geomagneti c indi ces are w idely used to represent the globa l nature or disturbances associated with solar terrestr ial phenomena. Geomagnetic observa tories

around the globe have the regular recordings or the varia ti ons in the geomagnetic fi eld at vari ous time reso lutions ranging from average hourly and one minute to one second . Considerabl e time and effort was put in since 1940 by various researche rsl (l - I ~ to develop an authentic index to represent the torrcstrial effects of the so lar particle radia tion. D iurnal variation pattern in the hori zon tal component o f the magneti c field from various observatori es is being used to derive various indices of geomagnetic activity on a planetary scale. The K index is one of the w idely used indices, computed from several station s distributed all over the globe, espec iall y mid and hi gh latitude locations. Currentl y, one minute digital magnetic data from many observatories are used to

LAKHINA & ALEX: SPACE WEATHER RESEARCH IN INDI A 343

deri ve the near-real-time geo magnetic conditions. A quantitati ve measure of the magnetic characteristics is provided by the three hourly K index. A linear index derived from the quas i-logarithmic K index represents the equivalent amplitude by ak. The daily arithmetic means of the amplitudes of K and ak are expressed as Kp and AI' indices. The Kp as a global magnetic activity index is a representati ve of the stat ions mostly at subauroral latitudes and the locations mainly cover the northern hemisphere and the European continent.

The large-scale influence of the magnetosphere­so lar wind interaction is much stronger in the auroral zones as well. An index to project the intensity of the aurora-related geomagneti c ac tivity is the AE index. It is well es tabli shed that the major manifes tation of the geomagnetic phenomena, assoc iated with the injection of energeti c electrons and ions into the inner magnetosphere, is the formation of the westward storm ring current. Low latitude ground magnetic observa tory records show systematically the depression in the horizontal component in response to thi s westward fl owing zonal current system in the eq uatorial di stance of 4-6 Re ( I Rc=6370 km). Suigura l9 defined the index Ds! as an ensemble of magnetospheric and ionospheric fields detected at middle and low geo magneti c latitudes on the earth. This index normally depicts the strength of magneti c storm and is considered as a proxy for the strength of the sy mmetric co mponent of the ring curren t. The data used in the computati on of Ds! index are based on the observatori es located at low latitudes away from the subauroral zone and from equatorial electroj et regIOn.

Ex tensive use of automated magnetic observatori es and satellite links has made it possible for near-real­ti me di ssemination of magneti c measurements. Geo magneti c vari ati ons depict the role of electric currents of ionospheri c and magnetospheri c origins, and of electromagnetic waves in wide range of frequencies. Regul ar geo magnetic variati ons arc attributed mainl y to sources of ionospheri c tidal origin caused by the sun and moon. These forces induce an apprec iable magnitude of day- to-day variability in the geo magnetic fi eld . Perturbations in the magnetic fi eld vary in time scales of the order of a few minutes to some hours. The intensity of perturbation large ly varies with latitude, with enhanced magn itude at auroral lat itudes and with minimum in the mid­latitudes. However, the enhancement of thi s phenomenon over the equatorial lati tude is a special

feature attributed to the ionospheric conducti vity structure. These perturbations are mostly global in nature, but sometimes restri cted to high latitudes .

Understanding the changes in the equatorial electrojet in response to the electrody namics processes in volved in the coupling between solar wind, magnetosphere and ionosphere is of great scientific interest. This is due to the dynamo region electric fields being communicated to hi gher altitudes along the highly conducting geomagnetic field lines . Dynamics of thi s nature, in turn , affects the distribution of plasma, pl asma motions, temperatures, winds and other processes of the equatori al ionosphere extending to higher lat itudes. Studies based on ground magneti c data have shown consistent and near instantaneous response of equatorial electrojet variat ions to geomagneti c disturbances at hi gh latitudes20

.2 1

. Monitoring the upper atmosphere by coherent and incoherent backscatter radar observati ons has confirmed that the di sturbances in the dynamo region electric fields at equatorial lat itudes originate in the corresponding electro­dynamic disturbances at hi gh lat itudes22

.

5 Existing international forecast services

Solar and geophysical data are monitored in real time from a large number of ground-based observat ions and satellite sensors di stributed all over the world . The preliminary reports and forecasts are publi shed by Space Weather Operations (SWO) in Boulder jointly by NOAA and AFW A (Air Force Weather Agency). The ten warning centres of the Internati onal URSI (Union Radioscientific Internati onale) gram and World Days Serv ice (IUWDS) deal with the daily reports and forecas ts of geomagnetic activity. One regional warning centre (RWC) is being operated from National Phys ical Laboratory , New Delhi , as a part of the International Space Environment Service (ISES) chain, and it caters to the needs of Indian reg ion".I. The NOAA 's Space Environment Center (SEC) in Boulder, Colorado, is the official centre for forecast ing di sturbances and alerts to safeguard the people and equipments in the space environment. Space Environment Laboratory (SEL) of the NOAA centre is the prime agency, which undertakes the tas k of monitoring almost 1400 data streams that include solar, magnetospheric and ionospheric parameters. The launch of ACE and SOHO satellites in the Ll point orbit at about 240 earth rad ii (RJ has made the

344 INDIAN J RAD IO & SPACE PHYS, DECEMBER 2002

space warnings more accurate to provide advance warning on the space weather status almost an hour prior to the impact of the so lar ejecta that could produce geomagnetic storm.

Ex isting forecasting models are heav il y dependent on the geomagnetic data inputs from mid and high latitudes . The low latitude ionosphere is protected from direct impact of the hi gh energy particles and ionospheric storms are rarely observed in the low latitude regions. However, communicati ons at all frequency ranges are affec ted by space weather to a grcater ex tent. The HF communication is affected more often, as thi s frequency depends on the refl ec ti on fro m the ionosphere as signal carriers. Thus, the electron density fluctu ati ons associated with the irregul arities in the ioni zed atmosphere contribute to signal fading during hi ghly di sturbed conditions, resulting in the deterioration in HF communications. Estab li shing a study of well integrated and co­coordinated in vcs ti gational acti vi ties of real time geomagneti c, ionospheri c and satellite data, would come as a breakthrough in elucidating the complex dynamics of the low latitude space environment. It is well established that there ex ists a direct correlation between the time vari ations of IMF as measured by satellites and the ground magneti c measurements, suggesting the change of low latitude electri c fi elds or current in response to the varying interplanetary conditi ons. However, no effort was initiated in quanti fyi ng the cause and effect of the solar-telTes tri al re lati on from the low latitude observati ons.

It is des irable to make an attempt in thi s direc ti on by mainly focus ing on the day -to-day geomagnetic and ionospheri c vari ation charac teristics from the low latitude measurements in India, in conjunction with the hi gh and mid latitudes . It is indeed crucial , because the global geomagnetic acti vity index, DSI , is the resultant of the complex electrodynamics interacti on processes ori ginated from the magnetosphere-ionosphere coupling.

6 Infrastructure for space weather research in India

Several Institutions and Uni versity Departments havc been participating on various programmes assoc iated with solar phys ics, interplanetary pl as ma and magnetic fi eld , magnetospheric physics, ionos pheric phys ics and atmospheri c physics th at form backbone for the space weather programme. Most of the scienti sts have utilized solar, inter­planetary and magnetospheric data from various

NASA mI SS Ions from 1970 onwards, for modelling the medium and for the study of dynami cs and instabilities in these regions. On the ex perimental side, experti se for the HF Doppler radar, VH F, MST and Parti al Refl ection radars ex ist in the count ry. Several ionosonde and airglow experiments are being conducted to understand the ionospheri c irregul ariti es. Excellent facilities for monitoring the sun ex ist at solar observatory at Udaipur, Ooty, Kodaikanal and some other pl aces in the country. A bri ef summary of the exi sting infrastructure in the count ry fo r space weather related research acti viti es is given in Table I.

The Indian scientific community has parti cipated in a number of nati onal and internati onal programmes related to the dynami cs of the upper atmosphere and ionosphere-magnetosphere and interpl anetary medium characteri sti cs, like All India Coordinated Programme on Ionosphere-Thermosphere Studies (AI CPITS) , International Equatori al Electrojet Year (IEEY), Indian Solar-Ten·estrial Energy Programme (lSTEP), Internati onal Geosphere Biosphere Programme (IGBP), SROSS, Magsat, Oersted, Polar Cluster, etc. and is ready for the CRABEX. Several strong theoreti cal groups dealing with the problems of magneti c storms and substorms, solar wi nd-magneto­sphere-ionosphere coupling and wave-particle interactions ex ist in the country. Unfortunately, the acti vities and programmes of various Institutions/ Departments are independent of each other as far as the space weather is concerned. Hence, there is an urgent need to evo lve a national program me on space weather under ISRO, which will prov ide an umbrell a to the scientists from national laboratori es, and U ni versiti es to carry out relevant ac ti vi ti es in a cohesive manner. It would also generate lots of interest among the researchers from the uni versities to accelerate or reorient their research effo rts toward space weather.

7 Space weather programme: Main science and application oriented objectives

The applicati on oriented objecti ves of the space weather programme are:

(i) Energization and lIlJection of ionospheric oxygen ions into ring current system and decay of storm-time ring current.

(ii ) To develop computer simulati ons of spacecraft charging.

(iii ) Geomagnetic activity predictions with di fferent time scales using data fro m Indian observatories.

LAKHINA & ALEX: SPACE WEATHER RESEARCH IN INDIA 345

Table I- Infrastructure availabl e in the country for space weather related acti viti es

Organ iza ti ons/U n i versi ties

And hra University. Waltair

Banaras Hi ndu Uni vcrsity

B~II'aktulia University. Bhopa l

Bhabha Atomic Research Centre. NRL. Trombay

Ind ian In stitute of Astrophys ics. Banga lore

Ind ian Institute of Geo magnetism. Mumbai

ISRO Satellit e: Ccntre. Uangalorc

Kerala Uni versity

Na ti onal Geophysical Research In stitute

Na ti onal MST Radar faci lity (N MRF). Tirupati

ati onal Ph ysica l Laboratory, New Delh i

Expe riments

Airglow photometer: Digital ionosonde: HF Doppler radar

Fabry- Perot spectro­photometer; Dual frequency microwave radi ometer: ELF, YLF ex periments by whi stler observations

Radi o beacon studies; Whi stler measurements

Cerenkov telescope at MI.Abu

Digital magnetometer: Di gital ionosonde

Network of II magneti c observatories; Di gital f1u xgate magnetometer set-up at 6 obse rvatories: M F ( 1.9R MH z) radars at Tiruneveli and Kolh apur; Radio beacon ex periment s: Scanning photometer; Tilting photometer: / \11 sky imaging camera at Kolhapur; TEC deduced from GPS measurements; CRABEX Ex periment

Scannin g sky monitor (SSM ) for Indian Astronomy satellite; So lar X-ray spectrometer for GSLY:C RAB EX

HF Dopp ler radar data

Magnetometers at 2 locati ons

MST (53 MH z) radar at Gada nk i; Rayleigh lidar system

Di gital ionoso nde; GPS. Radi o beacon studi es; RPA experiment on SROSS-C2; SASCOM Data Celller Lidar: Laser heterodyne system

In vesti gati ons/acti vi ti es

Ionosphere- thermosphere study; E- and F-reg ion dynami cs

For measuring thermospheri c temperature and winds, air pOllution; Whistler studies ; Ionosphere magnetosphere dynami cs

Pl asma irregul arities; Ground based technique for probing the inner magnetosphere

Study of ga mma ray so urces and the cos mi c ray mass compositi on

Ionosphere-thermosphere coupling; Solar- terrestrial relationships

So lar-Terrestrial phys ics; Magnetic storms and substorms; Secu lar var iations: Geomagnetic activity; Forecasting and space weathcr; Theoretical and si mul ation studies on storm-substorms phenomena: Mesosphere winds. tides and planetary waves; Plasma irregulariti es; Monitoring ni ghtglow emi ss ions at different wavelengths; Atmospheri c g!'av ity waves and F-reg ion irregularit ies : lonosphere­thermosphere dynam ics and Ionospheri c tomography

To study the long term variability in bright X- ray sources for studi es of variable stars; To study X-ray flu x from sun over 2 keY to lOMe Y energy range; Ionospheric tomography

To study the ionospheri c plasma drift

Studies related to low latitude magnetic variati ons

Studi es of long peri od atmospheri c waves. ionospheri c irregu lari ties: Temperature profil es at 5-85 km altitude range

Ionospheri c plasma parameters and plasma irregularities; Total electron cOlllents; Di ssemination of data for global change related studies: Measurements of ozone. watervapour, etc,

346 INDIAN J RADIO & SPACE PHYS, DECEMBER 2002

Table I-Infrastructure available in the country for space weather related activities--Collld

Organizati ons/Universities

Osmania University , Hyderabad

Experiments

Ionospheric scintillation experiment

In vestigations/act i v i ties

Ionospheric irregularities

Physical Research Laboratory, Ahmedabad

High resolution IR Fabry-Perot spectrometer; Ionosonde; All sky imaging camera; Fabry-Perot spectrometer at Mt. Abu; Coherent rad io beacon experiment; Nd:YAG backscatter lidar at Mt. Abu

Observations of bright diffuse nebulae associated with star forming regions; Ionospheric plasma properties and ionospheric irregularities; Measurement of neutral thermospheric temperature and wind; Total electron content (TEC), ionospheric tomography; Vertical structure of atmospheric density and temperature around 90 km

Survey of India, Dehradun

Tala Institute of Fundamental Research (TIFR). Mumbai

One permanent magnetic observatory at Sabhawala

Ooty radio telescope; GMRT

For studying the low latitude current system, secular variation pattern

Observations of high resolution interpl anetary scintillations; Probing o f inner he liosphere fro m 0 .2- 0.8 AU by IPS

Udaipur Solar Observatory of PRL, Ahmedabad

GONG telescope; Sun photometer; Solar X-ray spectrometer;

To probe interior of the sun using helioseismology; To study solar eruption processes, the solar flares, CMEs, etc.; Observations of soft X-rays from the sun; Hu synoptic observation of solar activity

University of Rajkot , Gujarat

Vikram Sarabhai Space Centre, Tri vandrum

Full di sk telescope

ELF. VLF Measurements; Radio beacon experiments

HF and VHF Doppler radar; Dig ital ionosonde;

Electromagnetic wave propagation in the ionosphere and magnetosphere; Ionospheric irregulariti es

Measurements of Doppler velocities and spectral width to study the ionospheric irregularities:

Langmuir probe measurements; Rayle igh lidar

Ionospheric E- and F-region parameters; E-region plasma properties; Vertical structure of atmospheric density and temperature from 5 to 85 km

(iv) Evaluation of thermospheric wind induced effects vis-a-vis electrodynamic effects. These are intended to throw light on the neutral-plasma dynamics as well as the magnetospheric electric field effects at low latitudes.

(v) Development of models on ionospheric va riability including for storm-time conditions and ionospheric irregularities. Development models for ionospheric scintillations and time­delay models for use in SATCOM .

(v i) Development of thermospheric models for satellite drag for low earth orbiters for different storm intensities.

Some of the problems to be tackled In space weather predictions are the following:

(i) Long- term solar activity predictions which are Llsed in determining the satellite life times and optimization of orbital parameters of low orbiting satellites, and for HF communication planning.

(ii) Short-term solar activity (solar indices) predictions are necessary to aid in satellite tracking and also in updating long-term HF predictions.

(iii) Forecasts on solar flares (X-ray flares) are needed to give warning on sudden ionospheric disturbances(SIDs) .

(iv) Predicting the hazards to orbiting geostationary satellites due to solar energetic particles resulting in partial or permanent damage.

(v) Forecasts on geomagnetic storm occurrences are needed for their ionospheric and thermospheric effects. During storms, HF communications can be severely affected and can pose senous problems to orbiting satellites.

8 Conclusions The geographical location of India in the g lobal

scenario is ideal for monitoring the developments in the equatorial and low latitude dynamics and its associated effect in the global Sq current system,

LAKHINA & ALEX: SPACE WEATHER RESEARCH IN INDIA 347

equatorial ionization anomaly and equatorial and low latitude ionospheric irregul arities. The eXIstIng ex tensive network of magnetic observatories through Russia, from magnetic pole to peninsular India centred along 145 0 geomagnetic meridian , provides unique data set of magnetic variations from pole to dip equator. Various aspects of equatorial ionosphere like spread-F, bubbles, equatorial anomaly, ionospheric scintillations, etc . have been extensively investigated at several institutions24

-3o

. The availability of the VHF backscatter radar measurements with high time resolution and rocket launching facilities at Thumba and Sriharikota are extremely useful in provid ing the ionospheric parameters to supplement the ground-based magnetometer data. In addition to these, eXIstIng experimental facilities, such as measurements of ionospheric parameters from ionosonde observations, MST radar measurements, drift measurements from partial reflection radars, scintillation and airglow measurements are already operational at various institutions in India. Scientists at National Physical Laboratory, New Delhi , have been actively involved in developing ionospheric prediction models for the Indian region during quiet and di sturbed ionospheric conditions31

-34

. Contri­butions from all these areas towards formulating a co­ordinated programme for space weather mission would place the country in the global arena.

Monitoring the changes in the geomagnetic field on a continuous basis yields information on the electromagnetic state of the near and far space environment of the planet earth. Magnetic recordings are a comparati vely inexpensive method to moni tor the signatures associated with the large-scale currents generated in the ionosphere and magnetosphere of the earth. The magnetic measurements from the Indian longitudinal chain form a unique database in view of investi gating the ionosphere magnetosphere-coupling processes, as the en tire network can cover the locati ons spanning from equator to the north pole in the Indo-Russian longi tude.

Acknowledgements The authors have been benefited from the

discussion, on several occasions, with Dr B M Reddy and Dr 0 R Lakshmi on various aspects of space weather and space weather predictions.

References I Klein L W & Burlaga L F, J Geop!Jys Res (USA), 87 ( 1982)

6 13.

2 Kamide Y, Yokoyama N, Gonzalez W D, Tsurutani B T, Daglis I A, Brekke A & Masuda S, J Geophys Res (USA), 103 (1998) 6917.

3 Tsurutani B T, Kamide Y, Gonzalez W D & Lepping R P, Phys & Chem Earth (UK), 24 (1999),101.

4 Gonzalez W D, Joselyn J A, Kamide Y, Kroehl H W, Rostoker G, Tsurutani B T & Yasyliunas Y M, J Geophys Res (USA), 99 ( 1994) 5771.

5 Tsurutani B T & Gonzalez W D, Geophys MOllogr Ser (USA) , AGU 98 (1997) 77.

6 Tsurutani B T, Gonzalez W D, Lakhina G S & Alex S, J Geophys Res (USA) (2002) [in press].

7 Burlaga L F & Lepping R P, Planet & Space Sci (UK), 25 (1977) 1151.

8 Singer S, TrailS Am GeopiJys Ullion (USA), 38 ( 1957) 175. 9 McPherron R L, Rev Geophys Space Phys (USA) , 17 ( 1979)

657. 10 Rostoker G, Akasofu S I, Foster J, Greenwald R A, Kamide

Y, Kawasaki K, Lui AT Y, McPherron R L & Russell C T , J Geophys Res (USA), 85 (1980) 1663.

11 Iyemori T & Rao D R K, Ann Geophys (Frallce), 14 ( 1996) 608.

12 Daglis I A, Eos Trans Am Geophys Union (USA) , 78 ( 1997) 245.

13 Daglis I A, Space Sto rms and Space Weather Hazards, (K1uwer Academic Publishers, Netherlands), 2001, p.l .

14 Lanzerotti L J, Space Storms and Space Weather Hazards (Kluwer Academic Publishers, Netherlands), 2001.

15 Uberoi C, Earth 's Proximal Space: Plasma ElectrodYllamics and the Solar system (Uni versity Press (India) Ltd, Hyderabad), 2000.

16 Bartels J, Heck N H & Johnston H F, Terr Magn AOllos Electr(USA), 44 (1939) 411.

17 Chapman S & Bartels J, Geomagnetism, Vois I & If (Clarendon Press, Oxford) , 1940.

18 Mayaud P N, IAGA Bull (lUGG), Vo1.2 1, 1967.

19 Sugiura M, Alln Int Geophys Year (UK), 35 (1964) 945 . 20 Rastogi R G & Patel Y L, Proc III dian Acad Sci A, 82 ( 1975)

12 1. 2 1 Sastri J H, Rao J Y S Y & Ramesh K B, J Geophys Res

(USA), 98 (1993) 17,517. 22 Somayajulu Y Y, Reddy C A & Yiswanathan K S, Geophys

Res Leu (USA), 12 (1985) 473 . 23 Lakshmi D R & B M Reddy, Proc Indian Narl Sci Acad A ,

68 (2002) 1. 24 Alex S, Koparkar P Y & Rastogi R G, J Am lOs & Terr Phys

(UK), 51 ( 1989) 37 1. 25 Dabas R S & Reddy B M, Radio Sci (USA) , 25 ( 1990) 125. 26 Pathan B M, Koparkar P Y, Rastogi R G & Rao D R K, Alln

Geophys (France), 9 ( 199 1) 126. 27 Bhattacharya A, Radio Sci (USA), 34 ( 1999) 229. 28 Sridharan R, Alok Taori, Gurubaran S, Rajaram R &

Shepherd M G, J AtnlOs & Solar Terr Phys(UK), 61 ( 1999) 1131.

29 Gurubaran S & Rajaram R, Geophys Res Le/l (USA). 26 ( 1999) 111 3.

30 Jain A R, Jaya Rao Y & Mydhili N S, J Atlllos & Solar Terr Phys (UK), 63 (2001) 1455.

3 1 Lakshmi D R, Reddy B M & Shastri S, Illdiall J Radio & Space Phys 12 ( 1983) 11 8.

348 INDIAN J RADIO & SPACE PHYS, DECEMB ER 2002

32 Reddy B M, Aggarwal S, Lakshmi DR, Shastri S & Mitra A P, Solar Terreslrial PrediCliril/ Proceedillgs, ed ited by R.F. Don ncly (US Dept. of Commerce, USA ) Vo l I, 1979, p. 11 8.

33 Reddy B M. Lakshmi D R, Aggarwa l S & Shastri S, /-falldboo/.: Oil Rarlio Propagrlliril/ j(iI' Tropical allrl

Sl/blropical COl/lllries, edited by A P Mitra. B M Reddy, S M Radicella, J 0 Oyi nloye & S Feng (U RSI ). 1987, p. 185.

34 Lakshllli D R, Veenadhari B, Dabas R S & Reddy 13 M. Ailil Ceop" ys (Fra llce), 15 ( 1997) 306.