-
This study aims to quantify the solar wind charge-exchange (SWCX) X-ray emission factors (denoted as α-value) and their dependence on solar wind parameters, solar activity cycles, and solar wind origins. By analyzing 13 years (1998{2011) of in situ measurements from the Advanced Composition Explorer (ACE) spacecraft, we investigate the statistical correlations between solar wind ionization states, elemental abundances (particularly oxygen), and bulk plasma parameters (proton speed, density). The derived α-values are critical for interpreting the data from Solar wind and Magnetosphere Interaction Linker Explorer (SMILE), and disentangling SWCX foreground emissions from diffuse astrophysical X-ray sources observed by Einstein Probe (EP) and proposed DIffuse X-ray Explorer (DIXE) payload on Chinese Space Station. This work analyzed high-resolution solar wind ion composition data and plasma parameters from ACE. Events were categorized by solar wind origin (coronal holes, streamers, interplanetary coronal mass ejections (ICMEs)) and solar cycle phase (minimum vs maximum). α-value, defined as the total soft X-ray photon emission cross section per solar wind proton, was computed using an updated charge-exchange model incorporating state-resolved cross-sections for highly charged ions. The model accounts for velocity-dependent cross-section of solar wind-neutral interaction. Statistical method and bin-averaging techniques were applied to extract correlations between α, solar wind speed (vsw), proton density (np), and oxygen abundance. The main results are:
1. Ionization state dynamics: A strong anti-correlation exists between solar wind ionization degree and bulk speed: high-speed wind (>500 km/s) exhibit lower ionization states compared to slow wind (<400 km/s).
2. Elemental abundance trends: Oxygen abundance ([O/H]) anti-correlates with np: denser solar wind plasmas (np > 13 cm-3) exhibit 30-50% lower [O/H], suggesting fractionation processes during plasma acceleration. No significant speed dependence of [O/H] was observed, contrasting with earlier studies.
3. Emission factor (α-value) behavior: α-value decreases rapidly with increasing np and stabilizes for np > 13 cm-3. Conversely, α-value increases gradually with vsw up to 430 km/s, beyond which it plateaus (Fig. 5). ICME-associated α exceeds streamer and coronal hole values by 35-60%, attributed to higher averaged ionic state in transient ejecta. Solar maximum α (2000-2002) is 1.3-2.7 times higher than solar minimum (2008-2010), reflecting cycle-dependent ion composition changes.
By bridging in situ solar wind measurements and X-ray emission physics, this work advances the capability to diagnose both solar wind-magnetosphere coupling and the diffuse X-ray background. The validated α-value will benefit data analysis for China’s space projects in the 2020s, for examples SMILE, DIXE and EP.-
Keywords:
- solar wind /
- charge-exchange /
- X-ray emission factor
-
[1] Snowden S L, Freyberg M J, Plucinsky P P, Schmitt J H M M, Trümper J, Voges W, Edgar R J, McCammon D & Sanders W T 1995 Astrophys. J. 454643
[2] Snowden S L, Egger R, Freyberg M J, McCammon D, Plucinsky P P, Sanders W T, Schmitt J H M M, Trümper J & Voges W 1997 Astrophys. J. 485125
[3] Freyberg M J 1994 The Local Bubble and Beyond 1113
[4] Lisse C M, Dennerl K, Englhauser J, Harden M, Marshall F E, Mumma M J, Petre R, Pye J P, Ricketts M J, Schmitt J, Trümper J & West R G 1996 Science 274205
[5] Cravens T E 1997 Gelphys. Res. Lett. 24105
[6] Cox D P 1998 Ed. by Breitschwerdt D, Freyberg M J, Trümper J 1998 Proceedings of the IAU Colloquium No. 166 Garching, Germany, April 21-251997 p121会议文集
[7] Cravens T E 2000 Astrophys. J. 532 L153
[8] Wargelin B J, Markevitch M, Juda M, Kharchenko V, Edgar R & Dalgarno A 2004 Astrophys. J. 607596
[9] Bhardwaj A, Gladstone G R, Elsner R F, Waite J H, Grodent D, Cravens T E, Howell R R, Metzger A E, Ostgaard N, Maurellis A N, Johnson R E, Weisskopf M C, Majeed T, Ford P G Tennant A F, Clarke J T, Lewis W S, Hurley K C, Crary F J, Feigelson E D, Garmire G P, Young D T, Dougherty M K, Espinose S A & Jahn J M 2002 Proc. ESLAB 36 Symposium, ‘Earth-Like Planets and Moons’ 215
[10] Robertson I P & Cravens T E 2003 Gelphys. Res. Lett. 301439(22-1)
[11] Sembay S, Alme A L, Agnolon D, Arnold T, Beardmore A, Belen Balado Margeli A B, Bicknell C, Bouldin C, Branduardi-Raymont G, Crawford T, Breuer J P, Buggey T, Butcher G, Canchal R, Carter J A, Cheney A, Collado-Vega Y, Connor H, Crawford T, Eaton N, Feldman C, Forsyth C, Frantzen T, Galgóczi G, Garcia J, Genov G Y, Gordillo C, Gröbelbauer H P, Guedel M, Guo Y, Hailey M, Hall D, Hampson R, Hasiba J, Hetherington O, Holland A, Hsieh S Y, Hubbard M W J, Jeszenszky H, Jones M, Kennedy T, Koch-Mehrin K, Kögel S, Krucker S, Kuntz K D, Laky G, Lylyund O, Martindale A, Mas Hesse J M, Nakamura R, Oksavik K, Østgaard N, Ottacher H, Ottensamer R, Pagani C, Parsons S, Patel P, Pearson J, Peikert G, Porter F S, Pouliantis T, Qureshi B H, Raab W, Randall G, Read A M, Roque N M M, Rostad M E, Runciman C, Sachdev S, Samsonov A, Soman M, Sibeck D, Smit S, Søndergard J, Speight R, Stavland S, Steller M, Sun T, Thornhill J, Thomas W, Ullaland K, Walsh B, Walton D, Wang C & Yang S 2024 Earth & Planetary Phys. 85
[12] Beiersdorfer P, Boyce K R, Brown G V, Chen H, Kahn S M, Kelley R L, May M, Olson R E, Porter F S, Stahle C K & Tillotson W A 2003 Science 3001558
[13] Zhang R T, Liao T, Zhang C J, Zhou L P, Guo D L, Gao Y, Gu L Y, Zhu X L, Zhang S F & Ma X 2023 Mon. Not. R. Astron. Soc. 5201417
[14] Jin H, Mao J J, Chen L B, Chen N H, Cui W, Gao B, Li J J, Li X F, Liu J J, Quan J, Jiang C Y, Wang G L, Wang L, Wang Q, Wang S F, Xiao A M & Zhang S 2024 J. Low Temperature Phys. 215256
[15] Sun T R, Connor H, Samsonov A 2024 Earth & Planetary Phys. 81
[16] Schwadron N A & Cravens T E 2000 Astrophys. J. 544558
[17] Smith R K, Foster A R & Brickhouse N S 2012 Astron. Nachr 333301
[18] Gu L Y, Kaastra J & Raassen A J J 2016 A&A 588 A52
[19] Cumbee R, Stancil P & Mcilvane S 2021 American Astronomical Society Meeting 23812601
[20] Liang G Y, Li F, Wang F L, Wu Y, Zhong J Y & Zhao G 2014 Astrophys. J. 783124
[21] Liang G Y, Zhu X L, Wei H G, Yuan D W, Zhong J Y, Wu Y, Hutton R, Cui W, Ma X W & Zhao G 2021 Mon. Not. R. Astron. Soc. 5082194
[22] Whittaker I C & Sembay S 2016 Gelphys. Res. Lett. 437328
[23] Koutroumpa D 2024 Earth & Planetary Phys. 8105
[24] Liang G Y, Sun T R, Lu H Y, Zhu X L, Wu Y, Li S B, Wei H G, Yuan D W, Zhong J Y, Cui W, Ma X W & Zhao G 2023, Astrophys. J. 94385
[25] Midha J M & Gupta S C 1994 J. Quant. Spectrosc. Radiat. Transfer 52897
[26] Wargelin B J, Beiersdorfer P & Brown G V 2008 Can. J. Phys. 86151
[27] Zhang R T, Seely D G, Andrianarijaona V M, Draganić I N & Havener C C 2022 Astrophys. J. 9311
[28] Wu Y, Stancil P C, Schultz D R, Hui Y, Liebermann H P & Buenker R J 2012 J. Phs. B: At. Mol. Opt. Phys. bf 45235201
[29] Nolte J L, Stancil P C, Liebermann H P, Buenker R J, Hui Y & Schultz D R 2012 J. Phs. B: At. Mol. Opt. Phys. 45245202
[30] Liu L, Wu Y, Wang J G & Janev R K 2022 At. Data & Nuclear Data Tables 143101464
[31] Royal Observatory of Belgium,on-line Sunspot Number catalogue ‘1998-2012’ http://www.sidc.be/SILSO/, 00
[32] Landi E, Gruesbeck J R, Lepri S T, Zurbuchen T H & Fisk L A 2012 Astrophys. J. 76148
[33] Zhao L, Zurbuchen T H & Fisk L A 2009 Gelphys. Res. Lett. 36 L14104
[34] Zhao L, Landi E, Lepri S T, Kocher M, Zurbuchen T H, Fisk L A, & Raines M J 2017 Astrophys. J. Supp. Ser. 2284
[35] Zhang C, Ling Z X, Sun X J, Sun S L, Liu Y, Li Z D, Xue Y L, Chen Y F, Dai Y F, Jia Z Q, Liu H Y, Zhang X F, Zhang Y H, Zhang S N, Chen F S, Cheng Z W, Fu W, Han Y X, Li H, Li J F, Li Y, Liu P R, Ma X H, Tang Y J, Wang C B, Xie R J, Yan A L, Zhang Q, Jiang B W, Jin G, Li L H, Qiu X B, Su D T, Sun J N, Xu Z, Zhang S K, Zhang Z, Zhang N, Bi X Z, Cai Z M, He J W, Liu H Q, Zhu X C, Cheng H Q, Cui C Z, Fan D W, Hu H B, Huang M H, Jin C C, Li D Y, Pan H W, Wang W X, Xu Y F, Yang X, Zhang B, Zhang M, Zhang W D, Zhao D H, Bai M, Ji Z, Liu Y R, Ma F L, Su J, Tong J Z, Wang Y S, Zhao Z J, Feldman C, O’Brien P, Osborne J P, Willingale R, Burwitz V, Hartner G, Langmeier A, Müller T, Rukdee S, Schmidt T, Kuulkers E & Yuan W 2022 Astrophys. J. Lett. 9412
Metrics
- Abstract views: 120
- PDF Downloads: 0
- Cited By: 0
下载:
