Results 61 to 70 of about 37,593 (223)

Solar photosphere magnetization [PDF]

Astronomy & Astrophysics, 2020
Context.A recent review shows that observations performed with different telescopes, spectral lines, and interpretation methods all agree about a vertical magnetic field gradient in solar active regions on the order of 3 G km−1, when a horizontal magnetic field gradient of only 0.3 G km−1is found.
openaire   +6 more sources

Periodic Density Structures Observed in Ulysses Data: First Results

Journal of Geophysical Research: Space Physics, Volume 131, Issue 3, March 2026.
Abstract Periodic density structures (PDSs) are advecting quasi‐periodic (periodicities between several minutes and several hours) density enhancements observed in the solar wind and corona. There is strong evidence that PDSs are formed at the Sun.
Brent M. Randol, Nicholeen Viall, Larry Kepko, Simone Di Matteo   +3 more
wiley   +1 more source

Investigation of Phase Shift and Travel Time of Acoustic Waves in the Lower Solar Atmosphere Using Multiheight Velocities

The Astrophysical Journal
We report and discuss the phase shift and phase travel time of low-frequency ( ν < 5.0 mHz) acoustic waves estimated within the photosphere and photosphere–chromosphere interface regions, utilizing multiheight velocities in the quiet Sun.
Hirdesh Kumar, Brajesh Kumar, Shibu K. Mathew, A. Raja Bayanna, S. P. Rajaguru   +4 more
doaj   +1 more source

Doppler shift oscillations in solar spicules

, 2007
Consecutive height series of Ha spectra in solar limb spicules taken on the 53 cm coronagraph of Abastumani Astrophysical Observatory at the heights of 3800-8700 km above the photosphere have been analyzed.
Ballester, Beckers, De Pontieu, De Pontieu, de Wijn, DeForest, E. Khutsishvili, Edwin, G. Ramishvili, Hasan, Hollweg, Katsiyannis, Khutsishvili, Kukhianidze, Kulidzanishvili, Molowny-Horas, Nakariakov, Nikolsky, Roberts, Singh, Spruit, Sterling, T. V. Zaqarashvili, Trujillo Bueno, V. Kukhianidze, Wunnenberg, Xia, Zaqarashvili, Zaqarashvili, Zaqarashvili   +29 more
core   +1 more source

A spectropolarimetric view on the nature of the peculiar Type I SN 2005hk [PDF]

, 2010
We report two spectropolarimetric observations of SN 2005hk, which is a close copy of the "very peculiar" SN 2002cx, showing low peak luminosity, slow decline, high ionization near peak and an unusually low expansion velocity of only about 7,000 km s^-1.
Baade, D., Clocchiatti, A., Hoeflich, P., Maund, J. R., Patat, F., Quinn, J., Wang, L., Wheeler, J. C., Zelaya, P.   +8 more
core   +4 more sources

On the Freeze‐In Distance of Solar Wind Fluid Entropy Variability in the Corona

Journal of Geophysical Research: Space Physics, Volume 131, Issue 3, March 2026.
Abstract The strong correlation between solar wind entropy and the frozen‐in ion charge state ratio O7+/O6+ ${\mathrm{O}}^{7+}/{\mathrm{O}}^{6+}$ indicates that entropy variability on timescales of hours or longer is preserved from its solar source. This prompts the question: where in the solar atmosphere does this entropy variability come from, and at
Aidan J. Nakhleh, Nicholeen M. Viall, Susan T. Lepri, Jim M. Raines   +3 more
wiley   +1 more source

THE SUN’S PHOTOSPHERIC CONVECTION SPECTRUM [PDF]

The Astrophysical Journal, 2015
Spectra of the cellular photospheric flows are determined from full-disk Doppler velocity observations acquired by the Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics Observatory (SDO) spacecraft. Three different analysis methods are used to separately determine spectral coefficients representing the poloidal flows, the toroidal
David H. Hathaway, Thibaud Teil, Aimee A. Norton, Irina Kitiashvili   +3 more
openaire   +2 more sources

Height dependence of the penumbral fine-scale structure in the inner solar atmosphere [PDF]

, 2018
We studied the physical parameters of the penumbra in a large and fully-developed sunspot, one of the largest over the last two solar cycles, by using full-Stokes measurements taken at the photospheric Fe I 617.3 nm and chromospheric Ca II 854.2 nm lines
Ermolli, I., Giorgi, F., Guglielmino, S. L., Jafarzadeh, S., Murabito, Mariarita, Romano, P., Socas-Navarro, H., Stangalini, M., Zuccarello, F.   +8 more
core   +2 more sources

A New Method for Probabilistic Spatiotemporal Forecasts of Solar Soft X‐Ray “S‐Class” (>X10) Superflares

Journal of Geophysical Research: Space Physics, Volume 131, Issue 2, February 2026.
Abstract Solar superflares of S‐class (>X10 in soft X‐rays) pose extreme space weather hazards, yet their prediction remains a fundamental challenge owing to their rapid and transient natures and the limitations of conventional event‐based forecasts. We introduce for the first time, a probabilistic spatiotemporal framework designed to identify extended
V. M. Velasco Herrera, G. Velasco Herrera, W. Soon, A. Özgüç, N. Babynets, A. Tlatov, M. Švanda, S. Qiu, S. Baliunas, B. Kotan, G. González González, L. A. Bautista Flores, M. Pazos   +12 more
wiley   +1 more source

Photospheric Response to a Flare [PDF]

The Astrophysical Journal, 2018
Abstract Flares produce sudden and permanent changes in the horizontal photospheric magnetic field. In particular, flares generally produce increased magnetic shear in the photospheric field along the neutral line. Recent observations also show that flares can produce sudden photospheric motion.
Michael S. Wheatland, Donald B. Melrose, Alpha Mastrano   +2 more
openaire   +2 more sources