Title Relativistic Solar Particle Events of 19 th Solar Cycle: Modeling Study Yu.V. Balabin, E.V. Vashenuyk, B.B. Gvozdevsky Polar Geophysical Institute Apatity, Russia 21-st ECRS Ko š ice, Slovakia, 9-12 September, 2008

Abstract 19th solar cycle was marked by a number of large GLE (Ground Level Enhancement) events. The paper deals with a modeling analysis of three large GLEs, occurred within 1960: May 4, November 12 and 15. At this time there already existed a network of neutron monitor stations created for the IGY. With use the data, obtained by this network the characteristics of relativistic solar protons (RSP) were obtained and their dynamics studied during the GLE events of The spectra, obtained from ground based data, well agree with direct measurements on balloons simultaneously carried out by the group of A.N. Charakhchyan from the Lebedev Physical Institute as well as other research groups.

OUTLINE Short information about neutron monitor network existed in 19 solar cycle and data sources Results of relativistic solar cosmic ray events study with the GLE modeling.: The GLE 08: May 4, 1960 The GLE 10: November 12, 1960 The GLE 11: November 15, 1960

The GLE-8 on was connected to a flare of 3+; N13W90, H-alpha onset, UT, in the active region McMath The increase at neutron monitors started at UT. In the modeling analysis we used the data of 21 neutron monitors Increase profiles at selected neutron monitor stations. Points are the modeled responses

The derived anisotropy axis and pitch angle grid lines for solar proton flux at UT The asymptotic cones (1-20GV), for the following NM stations: Slm - Sulphur Mountain, Ber - Berkly, Chu - Churchill, DpR - Deep River, MtW - Mount Wilson, Els - Elsworth, Res - Resolute, Th - Thule, Hrs - Herstmonceux, Upp - Uppsala, Col - College.

a: increase profiles during the GLE May 4, 1960 at the neutron monitor stations: Ft Churchill (1) and Resolute (2); b: dynamics of derived pitch angle distributions; c: dynamics of derived energetic spectra in the double logarithmic scale and in the semi logarithmic one (d). Black points are the direct solar proton data balloon measurements. May 4, 1960

Three GLE: 10, 11, 12, on November 12, 15, and 20, 1960 were connected to the one active region, McMath 5925, crossing the solar disk from 5 to 18 November. GLE 10, was caused by a flare of importance 3, N27W04. The start and maximum in H-alpha: and UT. The increase at neutron monitors began at UT. At our modeling analysis we used the data of 44 neutron monitors. Increase profiles at selected neutron monitor stations. Points are the modeled responses

The derived anisotropy axis and pitch angle grid lines for solar proton flux during the first increase at UT, The asymptotic cones (1-20 GV), the title is placed at the 20 GV end, are shown for the following NM stations: Chi - Chicago, Dee - Deep River, MtW - Mt Washington, McM - Mc Murdo, Els - Elsworth, Maw - Mawson, Lee -Leeds, Upp - Uppsala, Lin - Lindau, Ker-Kerguelen, Th - Thule, Col - College.

Increase profiles during the GLE November 12, 1960 at the neutron monitor stations, a: Deep River(1) and Leeds (2); b: Munchen (3) and Jungfrau (4); c: dynamics of derived energetic spectra; d: dynamics of derived pitch angle distributions. Points at the fig. are the direct solar proton data obtained by balloon measurements over Churchill [2]. November 12, 1960

Increase profiles at a number neutron monitor stations during the GLE. Points are the modeled responses. The event (GLE 11), was related to a flare of importance 3, N27W04. The start and maximum in H-alpha: and UT. type II radio onset at UT and the GLE onset at ±5 UT [Cliver et al., 1982]. At our modeling analysis we used data of 42 neutron monitors

The derived anisotropy axis and pitch angle grid lines for solar proton flux at UT, The asymptotic cones for vertically incident particles (1-20 GV), the title is placed at the 20 GV end, are shown for the following NM stations: McM - Mc Murdo, MtW - Mount Washington, Col - College, Cli – Climax, Res - Resolute, Chi - Chicago, Thu - Thule, Els - Elsworth, Lee - Leeds, Maw - Mawson, Ner - Nera, Ker - Kerguelen.

a: Increase profiles during the GLE November 15, 1960 at the neutron monitor stations: Uppsala (1), College (2), and Leeds (3); b: dynamics of derived pitch angle distributions; c: dynamics of derived energetic spectra, points are direct solar proton data obtained by balloon measurements over Murmansk. November 15, 1960

Results With modern modeling technique employing the optimization methods and modern magnetosphere models characteristics of relativistic solar cosmic rays: rigidity (energy) spectrum, anisotropy axis and pitch angle distribution for the large events of 19 th solar cycle have been obtained and their dynamics. There is good agreement between derived from ground based data solar proton spectra with direct measurements in adjacent energy intervals on balloons and rockets

Aknowledgements In the paper we used the data of GLE database of Australian Antarctic Division (M. Duldig with colleagues), GLE database of IZMIRAN group (V.Yanke, E. Eroshenko, A. Belov). We are grateful to R. Buetikofer, E. Flueckiger and all other colleagues presented ground based NM data used in this work. The balloon data of Charakhchyan group were presented by G.Bazilevskaya and Yu.Stozhkov