19th European Cosmic Ray Symposium
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19th European Cosmic Ray Symposium. Magnetospheric effects in cosmic rays during the unique magnetic storm in November 2003. Belov A., Baisultanova L., Eroshenko E., Yanke V. (IZMIRAN, Russia), Mavromichalaki H. (Athens University, Greece),

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19th European Cosmic Ray Symposium

Magnetospheric effects in cosmic rays

during the unique magnetic storm in November 2003

Belov A.,

Baisultanova L.,

Eroshenko E.,

Yanke V. (IZMIRAN, Russia),

Mavromichalaki H. (Athens University, Greece),

Pchelkin V. (PGI, Russia)

e-mail: [email protected]

http://cr0.izmiran.rssi.ru/mosc/main.htm

2004, Florence, Italy


Abstract
Abstract

  • Cosmic ray variations of magnetospheric origin during the severe magnetic storm on 20 November 2003 are selected from ground level observation data by means of the global survey method. Planetary distribution of the cut off rigidity variations during this disturbed period was obtained on this basis. For this event a correlation between Dst index and cut off rigidity variation was defined for each cosmic ray station. The most essential shift in cutoff rigidities occurred while Dst index was around -465 nT. Geomagnetic effect in cosmic ray intensity at some stations reached 6-8%. Cutoff rigidity variations were also calculated using the last model of magnetosphere from Tsyganenko 2003. This magnetospheric effect seems to be the greatest one over the history of neutron monitor observations. Maximum changes of geomagnetic cutoff rigidities were recorded this time at unusual low latitudes corresponded to about 7-8 GV cutoff rigidity. The results can be used in the neutron monitor data correction for magnetospheric effects and for the more accurate modeling as well of the magnetospheric current system during strong geomagnetic storms.


Magnetospheric effect in cr on 20 11 03
Magnetospheric effect in CR on 20.11.03

Aurora in Athens.

FotoA. Ayiomamitis.http://www.perseus.gr/Astro-Aurorae-20031120-001.htm

Counting rate at different NMs uncorrected for magnetospheric effect. FD is moderate despite of severe magnetic storm


Data and method neutron monitors stations used in this analysis
DATA and METHODNeutron Monitors Stations used in this analysis

Global Survey Method (GSM):

1. Coupling coefficients- beyond the atmosphere;

2. Trajectory calculations-beyond magnetosphere ;

3. Spherical analysis-to select different harmonics;

Counting rate -> isotropic part+3D anisotropy

+magn+err:

Data from 39 NMs : 15 high latitudinal (<1.2 GV), 22 – mid latitude and 2 NMwith Rc>10GV


Comparison of obtained drc with dst index
Comparison of obtained dRc with Dst-index


Correlation between cut off rigidity variations drc and dst index
Correlation between cut off rigidity variations dRc and Dst-index


Latitudinal dependences of drc for each hour during event
Latitudinal dependences of dRc for each hour during event.

Maximum in latitudinal distribution of dRc is found around 7-8 GV (usually 3-4 GV) that means ring current to be located at 3R.


Comparison experimental results with calculations by the last tsyganenko model
Comparison experimental results with calculations by the last Tsyganenko model

dRc variations in dependence on cut-off rigidity in the maximum of geomagnetic storm 20.11.03, derived from experimental CR data (circles) and calculated by the Tsyganenko (T01storm) model (red).

1. Good agreement under Rc>6 GV;

2. Disagreement at Rc<6GV may be caused by inadequacy of model under great magnetospheric disturbances;

3. Experimental methods applied to other magnetic storms gives the classical latitudinal dRc variations with the maximum around 3-4GV


Compare current systems obtained directly from experimental data and current systems obtained from models T01s, M01, A03 for tow values of Dst -70 and -140 nT.

Currents from the model of Alexeev et al. [2001, 2003]

A03

Currents obtained from the database by Fairfield et al. 1994].

Currents obtained from the database Tsyganenko et al. [2003].


Main conclusions
Main conclusions data and current systems obtained from models T01s, M01, A03 for tow values of Dst -70 and -140 nT..

  • 1) At the beginning of extreme magnetic storm on 20 November 2003 a small magnetosphere effect in cosmic rays was recorded, whereas an exclusively large effect was derived during the main phase of this storm. This allowed the latitudinal distribution of the cut off rigidity variations to be obtained for each hour during the main and recovery phases of this magnetosphere storm very useful for analysis a dynamic of evolving and damping out of the ring current systems.

  • 2) The ring current system during magnetic storm on 20 November 2003 was at more close distance from Earth (apparently about 3 Earth’s radii) than it usually observed. As a consequence, maximal magnetosphere effect in CR was recorded at lower latitudes, but not at the mid latitude stations as usual. Maximum changes of the geomagnetic cut off rigidity were shifted due to this anomalous from 3-4 GV (usually) to 7-8 GV.

  • 3) The calculations of Rc changes performed for the last "storm" model T01s of the magnetospheric magnetic field [12] shows a good agreement between experimental and theoretical values for rigidities > 6 GV. Possibly, the model is not adequate for the greatest magnetospheric disturbances, this causes a discrepancy for lower rigidities.

  • 4) Further developing and extended variant of this work, whether another events are analyzed, can be found on http://cr0.izmiran.rssi.ru/GeoMagCR/main.htm .


Reference
Reference data and current systems obtained from models T01s, M01, A03 for tow values of Dst -70 and -140 nT.

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  • Tsyganenko N.A., Singer H.J., Kasper J.C. // J. Geophys. Res.. 2003. V. 108(A5). 1209. doi:10.1029/2002JA009808.

  • Pchelkin V.V., Vashenjuk E.V. // Izv. AN SSSR, Ser. Phys. Vol. 65(3), p. 416, 2001.

  • Maltsev Y. P., Ostapenko A. A., Pchelkin V. V. // “Predictions of the magnetospheric electric currents during superstorms”, Izv. AN SSSR, Ser. Phys. In press, 2004.

  • Fairfield, D. H., N. A. Tsyganenko, A. V. Usmanov, and M. V. Malkov, A large magnetosphere magnetic field database, J. Geophys. Res., 99, No A6, 11,319-11,326, 1994.

  • Tsyganenko, N. A., H. J. Singer, and J. C. Kasper, Storm-time distortion of the inner magnetosphere: How severe can it get? J. Geophys. Res., 108, No A5, 10.1029/2002JA009808, 2003.

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  • Martrosyan G., // “Magnetospheric effect of cosmic rays and rigidity variations”, Izv. AN SSSR. In press, 2004.


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