Sunspot and (inverse) Evershed Flow

The Evershed effect is named after the British John Evershed and is the radial flow of gas across the photospheric surface of the penumbra of a sunspot from the inner border with the umbra towards the outer edge. Evershed discoverd this back in 1909 when working at the  Kokaikanal Solar Observatory in the south of India. See also this video about the Evershed Effect. There is also an inverse Evershed flow (IEF) going in the opposite direction. 

Ref. C. Beck and D. P. Choudhary 2020 ApJ 891 119

Above sketch of the magnetic topology of a sunspot and the various wave and flow phenomena. Left panel: side view of a sunspot. The gray and green rectangles indicate photosphere and chromosphere. Gray and red lines indicate magnetic field lines. Orange lines and arrows show the wavefront and assumed propagation of global sunspot oscillations. Black and blue arrows highlight the direction of the EF and IEF. The apparent radial propagation of umbral and penumbral waves is indicated by green and purple arrows. Right panel: magnification of the assumed magnetic field vector and the flows in the penumbra inside the yellow rectangle of the left panel.

Ref D. P. Choudhary and C. Beck 2018 ApJ 859 139

Above figure of different flow scenarios. A: inverse Evershed flow (IEF) through a siphon flow mechanism. B: IEF caused by mass shedding of rising field lines. C: IEF through coronal rain. D: photospheric Evershed flow. Magnetic field lines in cyan are those that are most relevant for the IEF. The black rectangle indicates the formation height of the Ca ii IR line at 854.2 nm from the continuum-forming layers to a height of about 1 Mm.

Postage Stamp India - Evershed Effect

My picture from April 23, 2022 of Sunspot AR2993/94 showing the penumbra, umbra and fibril structure of the penumbra. 

Sunspot AR3007 with HMIBC overlap

Some more details about sunspot AR3007 from last sunday May 15, 2022: 

- sunspot number 3007(and 3012) containing 30 spots

- sunspot class EKC and 340MH

I made an overlap with a magnetic view (HMIBC) from NASA/SDO from the same period. 

Sunspot AR3007 - Granulation first try out

Image of sunspot AR3007 made on May 15, 2022. The picture was taken in the afternoon, no clouds but turbulence. My objective was to get details of the granulation. Some details are visible but I'm not satisfied and will try again. To prevent turbulence this needs to happen in the mornings. 

Setting : TAL200K f.8.5 with ASI290MM.

Filter : ND5.0 and barlow x2

Software : SharpCap Pro, AS3!, IMPPG and CS4.

Sunspot AR3007 in H-Alpha

Image of sunspot AR3007 in H-Alpha using SolarMaxIII 70/400 f/5.7 DS BF15 with ASI290MM.

Software: SharpCap Pro using seeing tool threshhold, AS3! (5%), IMPPG and CS4 (adding color R1.3; G0.44;B0.2; RGB1.8).

Observing the Photosphere and Solar imaging settings

Only recently I made progress in imaging the details of sunspots. This was achieved through :

    - imaging with a monochrome camera

    - imaging of the sun in the early morning to be ahead of turbulence

    - use of seeing monitor from SharpCap and applying threshhold

    - exposure time below 10ms

    - format imaging SER 16 bit

    - stacking limited to 5% best images

    - editing using IMPPG software

So, what can we see of the photoshere with a 200mm telescope :

    -  limb darkening

    -  sunspots 

    - (micro)pores

    - light bridges

    - granulation

    - faculae

    - umbral dots and dark nucleus

    - penumbral fibrils or filaments

    - penumbral grains

    - intergranular bright points

Using my image from april 23 with sunspot AR2993/94 I can identify many of the above mentioned solar features.

EHT will announce groundbreaking Milky Way Results

Next thursday May 12, the Event Horizon Telescope team is about to announce a groundbreaking Milky Way result. See live coverage via this link. 

European Solar Telescope - EST and QuEST

 

Some good information on the solar science can be found on the EST website. See for more solar science this link.

Personally I like the QuEST video's (see this link) which provide an historic overview on :.

- Galileo Galilei - rotation of the Sun

- George Ellery Hale - magnetic fiels in sunspots

- Angelo Secchi - spicules 

- John and Mary Evershed - gas motions in penumbra, now known as Evershed effect

- Richard Carrington - solar flare