atmospheric radio soundings in argentina - effects of air density variations -
DESCRIPTION
Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft. Atmospheric Radio Soundings in Argentina - Effects of Air Density Variations -. Bianca Keilhauer. Tokyo, February 26th, 2004. Data Acquisition. Auger Fluorescence Detector measures longitudinal shower development - PowerPoint PPT PresentationTRANSCRIPT
Atmospheric Radio Soundings in Argentina
- Effects of Air Density Variations -
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Bianca Keilhauer Tokyo, February 26th, 2004
• Auger Fluorescence Detector measures longitudinal shower development
• Atmospheric parameter affect the development and detection at every height
⇒ Knowledge of atmospheric profiles is required
Radiosonde measurements in each season are performed:
61 successful launches in total Average reached altitude ≈ 20 km a.s.l. (maximum was 28 km a.s.l.) Roughly every 20 m a set of data (h, p, T, u, wind) Used DFM-97 GPS sondes (www.graw.de) Accuracy: T < 0.2 K p < 1.0 hPa (range 200 hPa to 1080 hPa) < 0.5 hPa (range 5 hPa to 200 hPa) u < 5%
Data Acquisition
Important Effects of Atmospheric Profiles
dx
dE
²cmgX kmh
X to h
transmission
1. Atmospheric depth to geom. height
2. Fluorescence light production
fl. yieldλ (p,T)
3. Fluorescence light transmission
τ (p,T)
h
dzzX
Fl. Yield
telescope
on the Auger FD shower data
height atmosph. depth
Fep
Fep
fluorescence photons
Geometrical Effect
particle number (x 109)
atm
osph
eric
dep
th (
g/cm
²)height (km a.s.l.)
10
8
6
5
4
3
2
1019eV / 0°
US Std. atmosphere
Fe
p
h
dzzX
atmospheric depth:
air density:
)(
)()(
zTR
Mzpz m
⇒ height and time dependent
Atmospheric Depth ProfilesAtmospheric Depth Profiles
Max. of Fe-ind. 1019eV, 60o shower in US-StdA
distortion of longitudinal shower profiles
shift of position of shower maximum
averaged measured profiles:
Difference in Atmospheric Depth
within seasons
summer,
January / February 2003
winter,
July / August 2003
Longitudinal Shower Development
- Energy Deposit -
⇒ Δhmax = 436 m between winter I and summer atmosphere
average of 100 simulated showers
⇒ same EAS in Ne(X) for all atmospheres
Fluorescence Yield
for a 1.4 MeV electron, vertical incidence
• EAS excites N2 – molecules in air
• de-excitation partly via fluorescence light emission
(λ ≈ 300 -400 nm)
• fl. yield ~ local energy deposit
Position of Shower Maximum
- Fluorescence Yield -
both EAS in US-StdA, 60°, 1019eV:
→ Δhmax= 800 m vertical height difference
7.6 km 8.4 km
both EAS 60°, 1019eV, p-ind. in summer, Fe-ind. in winter I:
→ Δhmax= 350 m vertical height difference
8.0 km
8.35 km
both 8.1 km
same EAS in Ne(X) for all atmospheres
Xmax distribution for Fe-ind. showers with
60°
N_entryMean in g/cm² RMS
1000 692 20.9
5000 713 26.1
⇒ increase of Xmax
distribution by approx. 25 %
same EAS in Ne(X) for all atmospheres
Summary
• Atmospheric conditions influence the: - Shower development - Fluorescence light emission - Light transmission
• EAS profiles are shifted and distorted: - Xmax position - Energy reconstruction- Distribution of Xmax broadened in dependence of incidence angle
(more important for Fe-ind. EAS than for p-ind. )
• Fluorescence yield is height and (p,T) - dependent
Difference of Atmospheric Depth Profiles
for pressure at ground: 825.0 ± 0.2 hPa, 829.0 ± 0.2 hPa, 826.0 ± 0.2 hPa, 834.5 ± 0.2 hPa
Atmospheric Depth Distribution at 2400 m for the individual profiles measured in
Argentina
N_entryMean in g/cm² RMS
61 783 4
15 785 2
11 783 5,5
17 781 4,7
18 783 2,2