[Paper Review] Relations between variability of the photospheric and interplanetary magnetic fields, solar wind and geomagnetic characteristics

E. Gavryuseva|arXiv (Cornell University)|Feb 9, 2018

Solar and Space Plasma Dynamics10 references3 citations

TL;DR

This study directly compares photospheric magnetic field variability across solar latitudes (1976–2004) with interplanetary and geomagnetic parameters using WSO and OMNI data, revealing two distinct groups of solar wind and geomagnetic responses: one driven by the interplanetary magnetic field (IMF) and solar wind parameters, and another linked to the IMF's Bz component and associated geomagnetic indices. The key finding is that solar magnetic field topology at different latitudes governs two distinct response pathways in heliospheric and geomagnetic variability, with no reliance on theoretical models or assumptions.

ABSTRACT

Large scale solar magnetic field topology has a great influence on the structure of the corona, heliosphera and geomagnetic perturbations. Data obtained over the last three solar cycles have been analysed to reveal the relationships between the photospheric field measured along the line of sight by the WSO group at 30 levels of heliolatitudes from -75 to 75 degrees and the interplanetary magnetic field The main aim of this first paper is to make a direct comparison between the basic structure and dynamics of the photospheric magnetic field and components and intensity of the interplanetary magnetic field % solar wind and geomagnetic parameters without using theoretical assumptions, models, physical expectations, etc. The second paper by Gavryuseva, 2018d presents the raports between different characteristics of the solar wind at the Earth orbit, and geomagnetic parameters provided by the OMNI team. % Data obtained over the last three solar cycles have been analysed % to reveal the relationships % between the photospheric field measured along the line of sight % by the WSO group % at heliolatitudes from -75 to 75 degrees averaged over one year % and the interplanetary magnetic field, different characteristics % of the solar wind at the Earth orbit, and geomagnetic parameters. % provided by the OMNI team. The heliospheric and geomagnetic data are found to be divided into two groups characterized by their response to variability of the solar magnetic field latitudinal structures on short and on long time scales.

Motivation & Objective

• To establish direct, model-free relationships between photospheric magnetic field (SMF) variability and interplanetary/geomagnetic parameters.
• To investigate how the latitudinal structure of the solar magnetic field influences solar wind and geomagnetic responses over long and short timescales.
• To identify distinct response patterns in solar wind and geomagnetic indices based on their sensitivity to different components of the photospheric and interplanetary magnetic fields.
• To determine the optimal time delays between SMF variations and their effects on interplanetary and geomagnetic parameters.
• To reveal the physical basis of solar-terrestrial coupling through empirical correlation analysis without theoretical assumptions.

Proposed method

• Utilized daily Wilcox Solar Observatory (WSO) data for line-of-sight photospheric magnetic field (SMF) at 30 heliolatitudes from -75° to 75°.
• Applied 1-year and 4-year running mean smoothing to separate long-term (SMF, SW) and short-term (FMF, FSW) variability components.
• Calculated residuals (FMF, FSW) as differences between 1-year and 4-year means to isolate short-term fluctuations.
• Computed cross-correlation coefficients (K_cor) between FMF at different latitudes and FSW parameters (e.g., B, Vp, Np, AE, DST) with optimized time delays.
• Analyzed latitudinal dependence of correlation coefficients to identify regions of the solar magnetic field most influential on interplanetary and geomagnetic responses.
• Used OMNI database data for interplanetary magnetic field (B, Bx, By, Bz), solar wind speed (Vp), proton density (Np), pressure (P), temperature (Tp), and geomagnetic indices (AE, Kp, DST).

Experimental results

Research questions

• RQ1 How does the latitudinal structure of the photospheric magnetic field influence the variability of interplanetary magnetic field and solar wind parameters?
• RQ2 What are the time delays between photospheric magnetic field variations and their effects on interplanetary and geomagnetic parameters?
• RQ3 Which solar wind and geomagnetic parameters show coherent responses to photospheric magnetic field variability across different latitudinal zones?
• RQ4 Are there distinct groups of interplanetary and geomagnetic parameters that respond similarly to photospheric magnetic field dynamics?
• RQ5 How do the responses of geomagnetic indices (AE, Kp, DST) correlate with the Bz and By components of the IMF and their latitudinal drivers?

Key findings

• Two distinct groups of solar wind and geomagnetic parameters were identified based on their correlation with photospheric magnetic field variability: one group dominated by IMF magnitude (B) and solar wind parameters (P, Np, Vp), and another by the Bz and By components.
• The correlation between photospheric field variability and IMF B component showed strong latitudinal dependence, peaking at ±25° and ±55° heliolatitude, indicating these regions as key sources of heliospheric field variability.
• The AE index, reflecting auroral electrojet activity, responded similarly to the B and P components of the IMF, suggesting a common driver from low-latitude photospheric fields.
• The Kp planetary index showed a distinct response pattern, correlating strongly with the Bz and By components of the IMF, indicating a dominant role of high-latitude (±55°) magnetic field structures in driving geomagnetic storms.
• The DST index, reflecting the ring current intensity, responded in an anti-correlated manner to Kp and Bx, with significant sensitivity to Bz and By variations originating from latitudes below ±55°.
• Short-term variability (FMF) of the photospheric field at ±55° latitudes showed the highest correlation with short-term solar wind and geomagnetic fluctuations, indicating these latitudes as primary sources of transient solar wind disturbances.