# How are sunspot numbers measured?

## How are sunspot numbers measured?

So, in the end, to calculate the sunspot number you’d count the number of sunspot groups and multiply that number by 10. You then add the result to the number of individual sunspots in all groups, and finally multiply that result by K.

What does the number of sunspots indicate?

If sunspots are active, more solar flares will result creating an increase in geomagnetic storm activity for Earth. Therefore during sunspot maximums, the Earth will see an increase in the Northern and Southern Lights and a possible disruption in radio transmissions and power grids.

### What is the average number of sunspots?

Yearly Mean Sunspot Numbers

Year Sunspot number
1745 11
1750 83.4 MAX
1755 9.6 min
1760 62.9

What is the average period for a sunspot cycle?

approximately 11-year
The number of sunspots increases and decreases over time in a regular, approximately 11-year cycle, called the sunspot cycle. The exact length of the cycle can vary. It has been as short as eight years and as long as fourteen, but the number of sunspots always increases over time, and then returns to low again.

## Where can I find a smoothed sunspot number?

Smoothed SSNs can currently be found from the Solar Influences Data Analysis Center (SIDC) of the Royal Observatory of Belgium at: http://sidc.oma.be/silso/FORECASTS/KFprediML.txt . They maintain the (predicted) SSN figures based on the Lincoln-McNish smoothing function.

When did they start using the sunspot number?

In 1966, tables of the FOT-MUF-HPF distribution as a function of local time at the transmitter, season, smoothed sunspot number (SSN) and geomagnetic latitude (of the transmit site) were incorporated in the first widely used HF ionospheric radio performance prediction program, ITSA-1 [Lucas and Haydon, 1966].

### What was the minimum sunspot number in solar cycle 24?

It began in December 2008 with a smoothed minimum sunspot number of 2.2. Activity was minimal until early 2010. It reached its maximum in April 2014 with a 23 months smoothed sunspot number of 81.8. This maximum value was substantially lower than other recent solar cycles, down to a level which had not been seen since cycles 12 to 15 (1878-1923).

Which is the correct sunspot number to use in VOACAP?

George Lane: In short, use the smoothed International Sunspot Number (SSN) values in VOACAP — or in any other interface program that uses VOACAP as their calculation engine.