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We investigate the variation in the mode parameters obtained from time series of length 9, 36, 72 and 108 days to understand the changes occurring on different time-scales. The regression analysis between frequency shifts and activity…

Solar and Stellar Astrophysics · Physics 2009-03-13 S. C. Tripathy , F. Hill , K. Jain , J. W. Leibacher

We present a seismological method to probe the solar atmosphere above sunspot umbrae with three-minute oscillations. Our technique allows us to estimate both the vertical distance between atmospheric layers and the wave-propagation speed…

Solar and Stellar Astrophysics · Physics 2017-12-27 A. S. Deres , S. A. Anfinogentov

The modeling of the heliosphere requires continuous three-dimensional solar wind data. The in-situ out-of-ecliptic measurements are very rare, so that other methods of solar wind detection are needed. We use the remote-sensing data of the…

Solar and Stellar Astrophysics · Physics 2015-10-27 Justyna M. Sokół , Paweł Swaczyna , Maciej Bzowski , Munetoshi Tokumaru

Coronal holes (CHs) are widely considered as the main sources of high-speed solar wind streams. We validate this thesis comparing the smoothed time series of solar wind speed measured by Advanced Composition Explorer (ACE) and various…

Solar and Stellar Astrophysics · Physics 2025-07-30 Egor Illarionov , Andrey Tlatov , Ivan Berezin , Nadezhda Skorbezh

The solar wind speed at Earth is one of the most important parameters regarding the effects of space weather on society. Thus far, most approaches for predicting the solar wind speed produce a single-value time series without uncertainty,…

Solar and Stellar Astrophysics · Physics 2026-03-13 Daniel E. da Silva , Yash Parlikar , Shaela I. Jones , Charles N. Arge

The dependence of the sources and properties of the near-Earth solar wind on solar cycle activity is an important issue in solar and space physics. We use the improved two-step mapping procedure that takes into account the initial…

Solar and Stellar Astrophysics · Physics 2024-07-02 Xinzheng Shi , Hui Fu , Zhenghua Huang , Limei Yan , Chi Ma , Chenxi Huangfu , Hongqiang Song , Lidong Xia

We present an analysis of solar wind dynamics based on Doppler spectral width measurements of X-band radio signals from the Japanese Akatsuki spacecraft. The dataset includes two solar conjunction occultation experiments conducted in 2016…

Solar and Stellar Astrophysics · Physics 2025-08-11 Keshav Aggarwal , R. K. Choudhary , Abhirup Datta , Takeshi Imamura

Current solar wind prediction is based on the Wang & Sheeley empirical relationship between the solar wind speed observed at 1 AU and the rate of magnetic flux tube expansion (FTE) between the photosphere and the inner corona, where FTE is…

Solar and Stellar Astrophysics · Physics 2020-10-21 Bala Poduval , Gordon Petrie , Luca Bertello

The solar wind (SW) is a supersonic outflow of plasma from the solar corona, with the latitudinal speed and density profiles varying with the solar activity. The SW protons charge exchange with the inflowing interstellar neutral atoms and…

Solar and Stellar Astrophysics · Physics 2023-07-27 C. Porowski , M. Bzowski , M. Tokumaru

High speed solar wind streams (HSSs) are very efficient drivers of geomagnetic activity at high latitudes. In this paper we use a recently developed $\Delta{H}$ parameter of geomagnetic activity, calculated from the night-side hourly…

Space Physics · Physics 2017-05-03 Renata Lukianova , Lauri Holappa , Kalevi Mursula

The long-term evolution of the Sun's rotation period cannot be directly observed, and is instead inferred from trends in the measured rotation periods of other Sun-like stars. Assuming the Sun spins-down as it ages, following rotation rate…

We present an analysis of interplanetary scintillation (IPS) observations conducted with the Arecibo 305-m radio telescope during the minimum phase at the end of solar cycle 24 and the onset of solar cycle 25. These observations span a…

Solar and Stellar Astrophysics · Physics 2025-02-25 P. K. Manoharan , C. J. Salter

The acceleration of the young solar wind is studied using the first 17 encounters of Parker Solar Probe. We identify wind intervals from different source regions: coronal hole (CH) interiors, streamers, and low Mach number boundary layers…

Solar and Stellar Astrophysics · Physics 2024-10-23 Yiming Jiao , Ying D. Liu , Wenshuai Cheng , Hao Ran , Rui Wang

We present a method to derive outflow velocities in the solar corona using different data sets including solar wind mass flux coming from the SWAN/SOHO instrument, electron density values from LASCO-C2 and interplanetary solar wind…

Astrophysics · Physics 2009-11-13 E. Quemerais , R. Lallement , D. Koutroumpa , P. Lamy

The 3D structure of solar wind and its evolution in time is needed for heliospheric modeling and interpretation of energetic neutral atoms observations. We present a model to retrieve the solar wind structure in heliolatitude and time using…

Solar and Stellar Astrophysics · Physics 2015-06-03 J. M. Sokol , M. Bzowski , M. Tokumaru , K. Fujiki , D. J. McComas

High-speed solar wind streams emanating from coronal holes are frequently impinging on the Earth's magnetosphere causing recurrent, medium-level geomagnetic storm activity. Modeling high-speed solar wind streams is thus an essential element…

Advancements in VLBI instrumentation, driven by the geodetic community's goal of achieving positioning accuracy of 1 mm and stability of 0.1 mm/y, have led to the development of new broadband systems. Here, we assess the potential of these…

Solar and Stellar Astrophysics · Physics 2025-04-23 A. Jaradat , G. Molera Calvés , J. Edwards , S. Ellingsen , T. McCarthy , J. Morgan

Connecting the solar wind observed throughout the heliosphere to its origins in the solar corona is one of the central aims of heliophysics. The variability in the magnetic field, bulk plasma, and heavy ion composition properties of the…

Solar and Stellar Astrophysics · Physics 2023-05-26 B. J. Lynch , N. M. Viall , A. K. Higginson , L. Zhao , S. T. Lepri , X. Sun

The determination of delay times of solar wind conditions at the sunward libration point to effects on Earth is investigated using mutual information. This measures the amount of information shared between two timeseries. We consider the…

Astrophysics · Physics 2007-05-23 T. K. March , S. C. Chapman , R. O. Dendy

In this work, we simulate the evolution of the solar wind along its main sequence lifetime and compute its thermal radio emission. To study the evolution of the solar wind, we use a sample of solar mass stars at different ages. All these…

Solar and Stellar Astrophysics · Physics 2019-06-17 D. Ó Fionnagáin , A. A. Vidotto , P. Petit , C. P. Folsom , S. V. Jeffers , S. C. Marsden , J. Morin , J. -D. do Nascimento