| 摘要: | 本研究針對2024年5月於AR 13664活躍區中接連發生的四起X級太陽閃焰（X1.0、X2.2、X1.1、X3.9）進行詳細分析，目的在於探討磁場參數與爆發活動的時序關聯，進一步驗證集約性參數（intensive quantities）EF/ET、|HJ|/|HV|、|HJ|/∅^′2作為閃焰是否伴隨日冕物質拋射預測指標的有效性。本研究使用SDO/HMI儀器提供的SHARP CEA磁圖當作非線性無力場（NLFFF）模型的輸入資料以重建三維磁場結構，再使用此三維磁場去計算廣延性參數（extensive parameters），如總磁能（Total magnetic energy, ET）、自由磁能（Free magnetic energy, EF）、勢磁能（Potential magnetic energy, EP）、相對磁螺度（Relative magnetic helicity, HV）、非勢磁螺度（Non-potential magnetic helicity, HJ）、勢磁螺度（Potential magnetic helicity, HP）、∅^′（half magnetic flux），並與集約性參數一起評估磁場的爆發潛能，閃焰爆發期間的事件分析以12分鐘的時間解析度進行短時間尺度分析，並以一個小時的時間解析度進行2024年5月7日至2024年5月10日的長時間尺度分析，空間積分範圍為整個活躍區往上300 Mm。分析結果顯示，四個X級事件皆表現出高度的集約性參數同步性，X1.0、X1.1、X3.9在爆發前的能量比值出現上升，隨後緩降的趨勢。X1.0及X1.1在磁螺度比值的時序資料上亦呈現爆發前上升隨後下降的趨勢。並且本研究的廣延性參數計算結果落在<ET> ≈ 1033 erg，<EＦ> ≈ 1033 erg，<EＰ> ≈ 1033 erg，<HV> ≈ 1044 Mx2，<HJ> ≈ 1043 Mx2，<HP> ≈ 1043 Mx2，<∅^′> ≈ 1022 Mx2，集約性參數的計算結果落在<EF/ET> > 0.3，<|HJ|/|HV|> > 0.4，<|HJ|/∅^′> > 0.3。值得注意的是，X2.2事件正經歷勢磁螺度符號轉換（helicity sign reversal），期間參數趨勢未明顯下降，推測與螺度反轉導致的磁重聯有關。相較Gupta et al. (2021)研究中所分析的多個活躍區，本研究活躍區的自由磁能與非勢磁螺度量級更高，分別為1033 erg 與1043 Mx²。
另外，本研究藉由繪製爆發前後的三維磁場線，觀察其形貌、扭曲程度與整體高度變化。三維磁場線結構顯示出爆發前磁場線多為低矮穩定結構（約100~200 Mm），爆發期間則有出現扭曲磁場線向上延伸、斷裂與重新連接的現象，多數事件在爆發結束後磁場線會回到初始高度，然而X3.9事件並未回復到初始高度，推測其原因為接續數日持續爆發數個強烈X級閃焰，因此整個活躍區進入高能量且不穩定的狀態。
綜合而言，本研究證實能量與磁螺度相關之集約性參數確實可作為X級閃焰是否伴隨日冕物質拋射的重要指標，並且X級閃焰的集約性參數具有極高的同步性，而三維磁場線在結構與高度的演化則提供了額外的物理依據，對未來太空天氣及磁場演化模型的發展具有重要意義
;This thesis analyzes four X-class solar flares (X1.0, X2.2, X1.1, X3.9) that erupted in May 2024 within NOAA Activity Region (AR) 13664. To analyze the relevance between magnetic field parameters and flare activity, this study utilized vector magnetograms from the SDO/HMI and reconstructed the three-dimensional coronal magnetic field by using the Nonlinear Force-Free Field (NLFFF) model. Based on the 3D magnetic field extrapolation, we calculated several extensive parameters including total magnetic energy ET, magnetic free energy EF, magnetic potential energy EP, relative helicity HV, non-potential helicity HJ, potential helicity HP, and half the unsigned magnetic flux Φ′. Furthermore, I evaluated intensive quantities: energy ratio EF/ET, helicity ratio ∣HJ∣/∣HV∣, and normalized nonpotential helicity ∣HJ∣/Φ′2.
I analyzed the parameters at two time resolutions: 12-minute cadence during solar flare explosion for short-term evolution, and 1-hour cadence for long-term trends. The volume of spatial integration spans from the photosphere up to 300 Mm above the active region. The analysis reveals strong synchronization across the intensive parameters during all four X-class flares, particularly the rise before explosion, and go decline later. The average values of the extensive parameters in this study fall in the following ranges: ⟨ET⟩ ≈ 1033 erg, ⟨EF⟩ ≈ 1033 erg, ⟨EP⟩ ≈ 1033 erg, ⟨HV⟩ ≈ 1044 Mx², ⟨HJ⟩ ≈ 1043 Mx², ⟨HP⟩ ≈ 1043 Mx², and ⟨Φ′⟩ ≈ 1022 Mx2. The intensive quantities show ⟨EF/ET⟩>0.3, ⟨∣HJ∣/∣HV∣⟩>0.4, and ⟨∣HJ∣/Φ′2⟩>0.3. Notably, because the X2.2 flare occurred during a helicity sign reversal (from negative to positive), the parameters did not exhibit a typical feature. Compared to the active regions analyzed by Gupta et al. (2021), the free magnetic energy and non-potential helicity in this study are at higher magnitudes (1033 erg and 1043 Mx², respectively), consistent with AR 13664 being one of the most active solar regions since the Halloween storms of 2003.
Additionally, this thesis uses AIA 1600 Å ultraviolet images to identify flare foot points, allowing the starting points of magnetic field lines to be set at locations overlapping with the positive magnetic polarity. The topology, twist, and elevation of field lines before and after flares were examined. The 3D magnetic field structure shows that pre-flare loops were generally low and stable (100–200 Mm), while during the flares, twisted field lines extended upward, exhibiting breakage and reconnection. In most events, the magnetic field lines returned to their original height after the explosion; however, in some cases, the structures remained elevated at 300–400 Mm after explosion, indicating a state of magnetic instability. Just like after the X3.9 flare, the active region entered a highly energized phase and produced several X-class flares over the following days.
In summary, the results of this thesis support the use of magnetic energy and helicity-based intensive parameters as reliable pre-flare indicators of major eruptive activity. Furthermore, the analysis of 3D magnetic field evolution provides complementary physical insight into the processes governing solar eruptions. These findings contribute to the development of more accurate coronal field modeling and improved forecasting capabilities for space weather phenomenon. |
