GLOBAL SURVEY METHOD: WHAT DO NEUTRON MONITORS SEE? Belov A.1, Eroshenko E.1, Abunin A. 1, Abunina M. 1, Yanke V. 1, Oleneva V.1, Mavromichalaki H.2, Papaioannou A IZMIRAN. Kaluzhskoe Ave., 4, Moscow, Troitsk, Russia, ; 2Faculty of Physics, National and Kapodistrian University of Athens, Athens, Greece; Ostend, 2015

CR variations as one of the important resources on Space Weather information

Neutron monitor network Since IGY NM invention (Simpson) – 5-6 now; Up to Super NM (NM64) -~ 55 operating now They cover whole the globe and can operatively present data in the Internet resources: 33 of them input data In the NMDB in real time (

NMs remain as the main and best detectors for the galactic CR, with some advantages before the others: Long time and continues registration; constant location; Long time set of homogenous data; High resolution of data accumulation; Large square of registration which provides high accuracy. The variation in the intensity provides valuable information on the heliospheric disturbances with characteristic scales of 0.01 to 100 AU, and processes in the heliosphere with characteristic times of 10**2-10**8 s. the energy range from hundreds MeV to hundreds GeV. These high energies represent an extension of the low-energy ranges measured on spacecraft

Problems Being created for studying primary CRs, NMs don’t record primary CRs, but only secondary particles generated in the atmosphere in the cascade processes. Change of the asymptotic directions Besides, GCR flux is affected by magnetosphere Need to have the global parameters of cosmic rays independent on the location of a point of observation on Earth, led to creation of special global methods which use data from a big number of the stations distributed on the globe.

Global survey method Counting rate variation for i - station can be written through the reception coefficients as: Eroshenko et al., Method of global survey (GSM) and corresponding tools for data preparation. Session 15, Poster 13. The parameters of GCR (A0, Ax, Ay, Az and gamma) in the interplanetary space were calculated by the data of NMN over the period for each hour. They are entered the database on Forbush effects (IZMIRAN) and used in different studies of solar-terrestrial relationships.

Two aspects: solar and galactic cosmic ray variations GLE profile finished much earlier than max flux in low energies occurred An example of the interplanetary disturbances created giant Forbush effects and severe magnetic storms in November 2004.

Example of behavior A0 and Axy together with interplanetary and geomagnetic parameters (December 2014)

Long term modulation of the CR A0 Variations of the CR monthly mean values and model calculation. Upper curves-contriubution of different parameters in the long-term modulation model.

Vector diagram of solar-diurnal CR anisotropy (Axy) during the obtained by hourly NMs data after GSM. Valuable information on the long-term changes of the heliomagnetosphere structure and GCR distribution. Dramatic behavior appears when study shorter time intervals. Axy vectors Regular recurrence 22-y magnetic cycle 11-year cycle in the amplitude

Coronal hole effect Gigantic coronal hole in March 2003 and its influence on solar wind, cosmic rays and geomagnetic activity Variation of the background cosmic rays due to solar wind disturbances generated by CME and/or coronal hole What is the Forbush effect?

Forbush decrease is the largest galactic CR variation 23th cycle The largest FE in the last cycle and over the history, and full 11-year CR modulation in the same scale.

Forbush effect is the most variable effect a1b1c1

10 biggest Forbush-effects in our data base occurred together with the strong magnetic storms (Kp-index >7 at least). As a rule it was severe or extreme magnetic storm (Oct. 2003, Aug. 1972). Forbush effects and magnetic storms Big (>7 %) FD without magnetic storm and small (<1%) with strong magnetic storm Cases FE without magnetic storm depend on the FE magnitude: ~50% if FE~1%; 2%; ~15% when FE >3%. FE>5% are almost not encountered without magnetic storm. July FD in November 2002

Sun Earth Modulation of Galactic Cosmic Rays by ICME

CR asymptotic angular distribution on October 2000, by the NMN data. Yellow circles correspond to increase and red one – to decrease of the CR variations. Circle size is proportional to the magnitude of CR variation. Precursory decrease apparently result from a “loss-cone” effect, in which a NM is magnetically connected to the cosmic ray-depleted region downstream the shock Pre-decrease within the narrow longitude range and wide pre-increase. Precursors of Forbush effects and magnetic storms

Asymptotic distribution of the CR variations on 3-5 October 1983 by NMN data Pre-decrease started to be observed ~6 hours prior the shock arrival Precursor -6 hours before the shock arrival (SSC) and start of the GLE and onset of magnetic storm in May 1990 The event on May 1990, presented as a longitude-time distribution. No obvious CR decrease, but a good example of precursor

The event on 3-5 October 1983 by NMN data. The sharp transfers from minimum to maximum CR variations occur most in the o  and o  longitude regions, near usual probably direction of the IMF. For protons of 10 GV rigidity on the quiet background of the IMF intensity (about 5 nT) the Larmor radius is about 0.04 AU. A shock at 500 km/s needs about 4 hours to travel this distance before arriving at Earth. So, these anomalies are most often observed in the last hours before shock arrival. The neutron monitor network can identify these signatures and therefore emit a warning of the imminent onset of a geomagnetic storm. Nonharmonical distribution of CR variations on the asymptotic longitude of NMs one hour before the shock arrival

Forbush effect is the most anisotropic effect It is during the FEs that the biggest anisotropy of the galactic CR is observed. For example, on February 15, 1978 in one of the greatest FE the first harmonic of CR anisotropy reached 10% (20 times bigger than normal). Here only equatorial component is plotted, but at the same time north- south component also varied in a wide range. Moreover, the second harmonic of anisotropy increased during the same hours up to ~10% that is two orders higher than its usual values. February 1978

Anisotropy of FD. February 1978.

Example of the fast event with well pronounced minimum in the CR density inside the MC Vector diagram and behavior of the CR density. Thin lines connect the equal time points on the vector diagram and density curve in every 6 hours. Vertical vectors correspond to the N-S anisotropy. Time passing by Earth the MC is shaded.

EAST WEST E E58, E E W W W79 CR density (A0) and anisotropy (Axy) during the FEs from remote sources

Ioannina Sept Compare of the vector anisotropy for the remote sources FEs in August 1989 (W60) and in July 1978 (E58) The increase of Axy is much more for FEs from the western source, but for east events on the Sun we see sharp change of Axy direction).

Statistical Analysis The storms in the solar wind, in the Earth’s magnetosphere and in the cosmic rays are closely related. Analysis of big amount events allowed the quantitative dependences to be found between the averaged characteristics of the interplanetary, geomagnetic and cosmic ray activity. These characteristics may be used in diagnostic of the solar activity manifestation Connection of the equatorial component of the CR anisotropy with the parameters of of the interplanetary space (Vsw, B, dA0) was studied on the large massive hourly data over the period of solar wind observation; In stable solar wind independently of SW velocity, a typical steady CR anisotropy exists with the magnitude of Axy=0.51÷0.53%. If some large enough change occur in the solar wind (increase velocity, changes A0 or strengthening IMF) the Axy increases significantly.

Statistical Analysis. Relation Axy to the solar wind velocity V and its changes dV for one hour. Counter isolines correspond to equal values of Axy Connection of Axy with the solar wind velocity V and IMF intensity B. Different colours mark different ranges of anisotropy (right scale).

Connection of Axy vector averaged by the cells with the size 1nTx0.05 %/hrs with the changes of CR density dA0 and IMF intensity B. In the report: Relation of the vector cosmic ray anisotropy to the parameters of solar wind, Abunina, M. et al., ESWW12, session 15 Little changes DA0 and B –zone of stable CR anisotropy Vector becomes unstable when one of these parameters (or both) significantly differs from norm. Vectors from the Sun are observed more often than to the Sun that is defined by the radial CR gradient

Statistical analysis Considering of many FEs shows that increase of amplitude and change of direction is a typical response of the 1-st order anisotropy to the shock and ejecta region. This essentially extends the capabilities of diagnosing of the solar wind structures. Statistical connections of the parameters of anisotropy with various states of interplanetary medium give the information about a degree of perturbation of this medium. Account of the size of Axy (separately or together with CR density variations A0) can change the probability of the quiet (Q) or disturbded (D) solar wind in tens and hundreds.

Main conclusion It is obvious that the variations of CR observed on Earth by neutron monitors give a valuable information about the processes happening on the Sun and in a heliosphere; Our task - to learn to take this information and to use it in the detailed analysis together with other available data; Especially important for space weather goals would be to make it feasible in real time by means of NMDB. Thank you