Efecto de las nubes magnéticas sobre la propagación de los rayos cósmicos

Transcripción

1 Efecto de las nubes magnéticas sobre la propagación de los rayos cósmicos J.J. Blanco, M.A. Hidalgo, J. Rodríguez-Pacheco, J. Medina y D. Arrazola Space Research Group, Universidad de Alcalá (Spain)

2 Helios 1 and Helios 2 were a pair of deep space probes developed by the Federal Republic of Germany (FRG) and NASA. The payload consisted of: fluxgate magnetometer electric and magnetic wave experiments Solar wind experiment Energetic particle experiment zodiacal-light experiment micrometeoroid experiment. The spin axis was normal to the ecliptic, with a spin rate of 1 rps.

3 Solar Ecliptic Coordinate System (SE) * Tierra en azul * H1 en verde * H2 en rojo

4 HELIOS 1: Start: 10. Dec End primary mission: 17. Apr End extended mission: Aug HELIOS 2: Start: 15. Jan End primary mission: 17. May 1976 End extended mission: 3. March 1980

5 E6 Cosmic Ray Experiment (PI: H. Kunow)

6 Data availability and capability with VIH

7

8 Electrons (MeV) Protons (MeV) Magnetic Field (nt) MagneticField orientation (longitude, elevation)

9 Electrons (MeV) Protons (MeV) Magnetic Field (nt) MagneticField orientation (longitude, elevation)

10 Electrons (MeV) Guard # >40 MeV Cerenkov # > 60 MeV Magnetic Field (nt) MagneticField orientation (longitude, elevation)

11 Data analysis Guard detector has been used to study particle decreases at energies above 60 MeV/nucleon (Cane et al., 1997, JGR) From January 1975 to 1979 Magnetic cloud: magnetic structure High field intensity Smooth rotation Plasma low temperature Fitted to a model (Hidalgo, 2003 JGR) Normalized counts to compare 28 events Divided into three categories: Types 1, 2 and 3 5 of them HELIOS observed by both

12 An analytical non-force-free model ( Hidalgo, 2003) j B =0 PARAMETERS OF THE MODEL - Parameters related to orientation of the cloud: the latitude with respect to the ecliptic plane, θ, the longitude in the ecliptic plane, φ, the minimum distance of the spacecraft to the cloud axis, y0 the cross-section orientation, z - Parameter related to the plasma behavior: α λ - Parameter related to the distortion of the cross section of the cloud: η - Parameter related to the expansion of the cross section of the cloud: t0 - The axial component of the magnetic field at the axis of the cloud By0

13 Type 1 Type 1 (12 events) The guard and the cerenkov detectors don't observe enhancements in their number of counts This event was observed by HELIOS 1 at AU.

14 Type 2 Type 2 (5 events) The guard and the cerenkov detectors show consecutive decreases in their number of counts This event was observed by HELIOS 1 at AU.

15 Type 3 Type 3 (11 events) The guard and the cerenkov detectors show enhancements in their number of counts This event was observed by HELIOS 1 at AU

16 Magnetic cloud effect on particle decreases

17 Magnetic cloud orientation effect on particle decreases

18 Dependences with the distance to Sun

19 Conclusions Decreases in count in the Cerenkov detector can be used as additional proxy to determine the MC limits Cerenkov detector gives some additional information to the guard detector in high (>60 MeV) energetic particle events Decreases use to be larger than MC passages No clear MC orientation effect on particle decreases None dominant parameter, probably combined effects

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