Introduction Solar Modulation at High Rigidity Cutoff Summary Cosmic Ray Modulation Observed by the Princess Sirindhorn Neutron Monitor at High Rigidity Cutoff P.-S. Mangeard, 1 J. Clem, 1 P. Evenson, 1 R. Pyle, 2 W. Mitthumsiri , 3 D. Ruffolo, 3 A. Sáiz, 3 T. Nutaro 4 1 Bartol Res. Inst. and Dept. of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA. 2 Pyle Consulting Group, Inc., St. Charles, IL 60174, USA. 3 Dept. of Physics, Fac. of Science, Mahidol University, Bangkok 10400, Thailand. 4 Dept. of Physics, Fac. of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand. 18 July 2017 Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 1
Introduction Solar Modulation at High Rigidity Cutoff Summary Overview Introduction 1 Solar Modulation as Seen by NMs The PSNM Station Solar Modulation at High Rigidity Cutoff 2 Observation by PSNM Comparison With Other NM Data Comparison With Heliospheric Measurements Summary 3 Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 2
Introduction Solar Modulation as Seen by NMs Solar Modulation at High Rigidity Cutoff The PSNM Station Summary Solar Modulation as Seen by Neutron Monitors http://neutronm.bartol.udel.edu/ 2 1 Moraal et al. (1989) Flat ( qA > 0) or peaked ( qA < 0) 1 modulation patterns 3 Spectral crossover of the DRF between 2 periods of qA < 0 and qA > 0 with similar modulation level Linear trend between modulation at high 3 and low cutoff Nuntiyakul et al. (2014) Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 3
Introduction Solar Modulation as Seen by NMs Solar Modulation at High Rigidity Cutoff The PSNM Station Summary The PSNM station 19 Apparent cutoff rigidity (GV) AHME: Ahmedabad qA+ qA- qA+ qA- qA+ qA- qA+ BUEN: Buenos Aeres KDIK CHAC: Chacaltaya 18 CORD: Cordoba DOIN DAEJ: Daejon 17 DARW: Darwin DOIN: Doi Inthanon AHME ESOI: ESOI-Tau (Israel) LAEP 16 FUKU: Fukushima KAMP HALE: Haleakala 15 HUAN: Huancayo KAMP: Kampala DARW KDIK: Kodaikanal 14 HUAN TIBT KULA: Kula Hawaii MAKA HALE LAEP: Lae Papua HALE KULA MAKA: Makapuu Point 13 CHAC MINA MINA: Mina Aguilar BP-28 neutron counter tubes with BF 3 PUTR MORI: Morioka 12 RIOD TKYO NORI: Mount Norikura NORI PUTR: Putre Incas At Doi Inthanon, Thailand, ∼ 2560 m CORD SEOU RIOD: Rio de Janeiro DAEJ 11 ESOI SEOU: Seoul BUEN FUKU SNTI: Santiago MORI SNTI Apparent rigidity cutoff: P c ∼ 17 . 3 GV 10 TIBT: Tibet TKYO: Tokyo 1950 1960 1970 1980 1990 2000 2010 P med ∼ 35 GV Year www.thaispaceweather.com Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 4
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Observation by PSNM 625 Doi Inthanon count rate (Hz) 620 615 610 605 600 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Count rates averaged per Carrington rotation. The variations of the rigidity cutoff are assumed negligible. Tropical climate: correction for variations of the water vapor pressure at the surface. Grey: All data. Black: Main Forbush decreases were removed. Note dips of 1-2 months, even with Forbush decreases removed. Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 5
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Observation by PSNM 625 Doi Inthanon count rate (Hz) 620 615 610 605 600 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Solar minimum maximum min? 200 Total Sunspot Number WDC-SILSO Mean 150 100 50 0 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Data V2.0 from http://www.sidc.be/silso/datafiles Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 6
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Observation by PSNM Polarity reversal 625 Doi Inthanon count rate (Hz) 620 615 610 605 600 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Solar minimum maximum min? T) µ Ba=(Bn-Bs)/2 magnetic field ( 50 WSO polar Bn 0 Bs 50 − 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Data from http://wso.stanford.edu/Polar.html Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 6
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Observation by PSNM Polarity reversal 625 Doi Inthanon count rate (Hz) 620 615 610 605 600 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Solar minimum maximum min? 1 Solar polarity qA < 0 with low solar activity (RED) 2 4-year plateau with full recoveries (BROWN) 3 Fast decrease of the count rate: ∼ 50% of the total modulation (GREEN). Synchronous with the increase of e + / e − measurements from PAMELA (Adriani et al. (2016)) 4 Solar polarity qA > 0 (BLUE) Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 6
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Comparison With McMurdo Data (1) Polarity reversal 625 Doi Inthanon count rate (Hz) 620 615 610 605 600 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Solar minimum maximum min? 300 McMurdo count rate (Hz) 290 280 270 260 250 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Distinct pattern during the period of high solar activity Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 7
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Comparison With McMurdo Data (2) Linear trends during low solar activity. Is there a change of 625 Doi Inthanon count rate (Hz) slope after the solar polarity a reversal? 620 4-year plateau Spectral hysteresis is observed qA<0 615 The fast decrease at DI is actually observed at 610 Fast drop at DI qA>0 McMurdo... 2007 Dec 9 to 2010 Apr 22 Loss of linearity for ∼ 4 years. 2010 Apr 22 to 2014 Feb 2 605 2014 Feb 2 to 2014 Nov 11 This was only during ∼ 1 year 2014 Nov 11 to 2017 Jan 7 250 260 270 280 290 300 ( ∼ 2000) for the previous solar McMurdo count rate (Hz) maximum (Nuntiyakul et al. (2014)). Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 8
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Comparison With McMurdo Data (3) Scatter plot for low solar 625 Doi Inthanon count rate (Hz) b qA<0, fall activity only R=1.000 620 s=0.61+/-0.05 The linear trend between count rates of NMs at different cutoff 615 qA>0 is now observed at ∼ 17 GV R=0.983 qA<0 s=0.49+/-0.02 R=0.948 610 The change of slope after the s=0.58+/-0.04 solar magnetic polarity reversal qA<0, rise R=1.000 605 confirms the observation from s=0.60+/-0.05 the latitude surveys 250 260 270 280 290 300 (Nuntiyakul et al. (2014)) McMurdo count rate (Hz) Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 9
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Comparison With McMurdo Data (3) Scatter plot for low solar 625 Doi Inthanon count rate (Hz) b qA<0, fall activity only R=1.000 620 s=0.61+/-0.05 The linear trend between count rates of NMs at different cutoff 615 qA>0 is now observed at ∼ 17 GV R=0.983 qA<0 s=0.49+/-0.02 R=0.948 610 The change of slope after the s=0.58+/-0.04 solar magnetic polarity reversal qA<0, rise R=1.000 605 confirms the observation from s=0.60+/-0.05 the latitude surveys 250 260 270 280 290 300 (Nuntiyakul et al. (2014)) McMurdo count rate (Hz) What about the crossover? We need more NMs at different rigidity cutoffs Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 9
Introduction Observation by PSNM Solar Modulation at High Rigidity Cutoff Comparison With Other NM Data Summary Comparison With Heliospheric Measurements Inadequacy of Modulation Parameter Derived From Low-Cutoff NM Data Modulations from the NMs at Almaty, McMurdo, and Newark using the method presented in Ghelfi et al. (2016, 2017) 625 Doi Inthanon count rate (Hz) 620 615 610 605 Observation 600 MC - - P =6.7 GV Φ Almaty c MC - - P =2.0 GV Φ Newark c 595 MC - - P =0.3 GV Φ McMurdo c 590 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 A single modulation parameter doesn’t allow one to reproduce the variations over the whole period at all cutoffs. Observed modulation at 6.7 GV is much more similar to that observed at DI than that at McMurdo Compatible with a crossover at 5-6 GV Pierre-Simon Mangeard (University of Delaware) 35th ICRC, 10-20 July 2017, Busan, South Korea 10
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