Simulating Properties of “Seasonal” Variability in Solar Activity And Space Weather Impacts

The Van-Allen Radiation belt electron
Wednesday, April 21, 2021

Solar short-term, quasi-annual variability within a decadal sunspot-cycle has recently been observed to strongly correlate with major class solar flares, resulting into quasi-periodic space weather “seasons”.

Superstrong photospheric magnetic fields in sunspot penumbrae

Graphic image showing a portion of the inner penumbra in the MURaM sunspot simulation
Friday, October 2, 2020

Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions.

Constraining nonlinear dynamo models using quasi-biennial oscillations from sunspot area data

Graphic depicting continuous wavelet spectra of the sunspot area (SSA)
Thursday, July 25, 2019

Solar magnetic activity exhibits variations with periods between 1.5–4 years, the so-called quasi-biennial oscillations (QBOs), in addition to the well-known 11-year Schwabe cycles. The solar dynamo is thought to be the responsible mechanism for the generation of the QBOs.

Recovery from Maunder-like Grand Minima in a Babcock–Leighton Solar Dynamo Model

Temporal variation of the smoothed sunspot number
Tuesday, September 4, 2018

The Sun occasionally goes through Maunder-like extended grand minima when its magnetic activity drops considerably from the normal activity level for several decades. Many possible theories have been proposed to explain the origin of these minima.

Ionospheric Electron Content during Solar Cycle 23

Comparison of measured to modeled global total electron content
Tuesday, March 13, 2018

Solomon & Qian show that solar minima are not all the same, and may have implications for understanding the Sun during the extended periods of very low activity known as “grand minima” that have sometimes occurred in the past, the best known of which was the Maunder Minimum during 1650–1700.

The longitudinal evolution of equatorial coronal holes

The evolution of the total daily (black) and hemispheric sunspot numbers
Thursday, December 28, 2017

In 2011, three satellites—the Solar-Terrestrial RElations Observatory (STEREO) A & B, and the Solar Dynamics Observatory (SDO)—were in a unique spatial alignment that allowed a 360 degree view of the Sun. This alignment lasted until 2014, the peak of solar cycle 24.

Evershed and Counter-Evershed Flows In Sunspot MHD Simulations

Field line connectivity and associated pressure perturbation image
Wednesday, December 13, 2017

There have been a number of reports in the literature of counter-Evershed flows in well developed sunspot penumbrae, i.e. flows directed towards the umbra.

What causes the "seasons" in space weather?

Oscillation between differential rotation kinetic energy (solid red curve) and perturbation Rossby waves kinetic energy (red dashed curve)

It is widely known that the Sun has 'spots'--dark areas on its surface that are well known to contain strong magnetic fields, much stronger than the Earth's field. The number of spots seen on the Sun waxes and wanes with a period of roughly eleven years, the 'solar cycle'.

Magnetic Buoyancy and Rotational Instabilities in the Tachocline

Instability domains in low and middle latitudes
Wednesday, January 17, 2018

Peter Gilman presents results from an analytical model for magnetic buoyancy and ro­tational instabilities in a full spherical shell tachocline that includes rotation. differential rotation close to that observed helioseismicly, and toroidal field.

Origins of the Ambient Solar Wind: Implication for Space Weather

Carrington rotation stack plots
Thursday, September 7, 2017

The Sun’s outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind.


Subscribe to RSS - Sunspots