Dr. Ahmed G. Abo-Khalil

Electrical Engineering Department

Sunspot

Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They correspond to concentrations of magnetic field that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere. Sunspots usually appear as pairs, with each spot having the opposite magnetic polarity of the other.[2]

Although they are at temperatures of roughly 3,000–4,500 K (2,700–4,200 °C), the contrast with the surrounding material at about 5,780 K (5,500 °C) leaves them clearly visible as dark spots, as the luminous intensity of a heated black body (closely approximated by the photosphere) is proportional to the fourth power of its temperature. If the sunspot were isolated from the surrounding photosphere it would be brighter than the Moon.[3] Sunspots expand and contract as they move across the surface of the Sun and can be as small as 16 kilometers (10 mi)[4] and as large as 160,000 kilometers (100,000 mi)[5] in diameter, making the larger ones visible from Earth without the aid of a telescope.[6] They may also travel at relative speeds ("proper motions") of a few hundred meters per second when they first emerge onto the solar photosphere.

Manifesting intense magnetic activity, sunspots host secondary phenomena such as coronal loops (prominences) and reconnection events. Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on stars other than the sun are commonly called starspots and both light and dark spots have been measured.

Office Hours

Monday 10 -2

Tuesday 10-12

Thursday 11-1

My Timetable

Contacts


email: a.abokhalil@mu.edu.sa

a_galal@yahoo.com

Phone: 2570

Welcome

Welcome To Faculty of Engineering

Almajmaah University

IEEE

Institute of Electrical and Electronics Engineers

http://www.ieee.org/

http://ieeexplore.ieee.org/Xplore/guesthome.jsp

http://ieee-ies.org/

http://www.ieee-pes.org/

http://www.pels.org/

Links of Interest

http://www.utk.edu/research/

http://science.doe.gov/grants/index.asp

http://www1.eere.energy.gov/vehiclesandfuels/

http://www.eere.energy.gov/


القران الكريم

http://quran.muslim-web.com/

Travel Web Sites

http://www.hotels.com/

http://www.orbitz.com/

http://www.hotwire.com/us/index.jsp

http://www.kayak.com/

Photovoltaic Operation


Wave Power

World's Simplest Electric Train



PeltierModule-JouleThief-Fridge

homemade Aircondition

Salt water battery


إحصائية الموقع

عدد الصفحات: 2880

البحوث والمحاضرات: 1292

الزيارات: 45509