The Ionosphere

Updated on May 3, 2018
unvrso profile image

An avid camper and hiker as well as writer and astronomy lover, Jose Juan Gutierrez has always been inspired by the sky

Earth´s Ionosphere

Earth´s Ionosphere
Earth´s Ionosphere | Source

What is the Ionosphere?

The ionosphere is the layer of the earth´s atmosphere that extends throughout the mesosphere, thermosphere and exosphere and starts at an altitude of about 60 km all the way up to about 800 km. It is so named because it´s a layer in the atmosphere where ions are present. While molecules composing the atmosphere are present in a combined state or neutral, in the ionosphere, these molecules are split or ionized by solar radiation (ultraviolet light). Its different regions are categorized as peaks of ionization levels, being denser based on altitude; the more higher they´re on the atmosphere, the more electrified they become.

To identify these layers or peaks or regions, they have been designated by distinct letters. E, which stands for electrified was the first historical designation made, as it was the first region discovered. The D region, which is the lowest one, and the F region, topmost region, were discovered later. There is another region designated with the letter C, but this region is not sufficiently ionized and therefore dosen´t have any real effect on radio communications.

Ionization of the Atmosphere

In the ionosphere extreme ultraviolet and x-ray solar radiation along with cosmic rays and charged particles ionize the atoms and molecules present, creating a region of positively charged ions and free electrons. it´s the free electrons which cause high frequency radio waves to be refracted and reflected back to the surface of the earth. The higher frequencies reflected depend on the density of free electrons in the ionosphere.

Cosmic rays originate in the sun but may also come from other bodies outside the solar system and are then known as galactic cosmic rays. They are high speed particles-atomic nucleus or electrons. This particles interact with the ionosphere at all times but most commonly at night.

Ionospheric Reflection

Ionospheric Reflection
Ionospheric Reflection | Source

Earth´s Upper Atmosphere-Ionosphere

This region in the atmosphere is continually ionized by solar radiation during the day and by cosmic rays during the night and allows the propagation of radio waves across the planet

The Ionospheric Layers

The ionosphere comprises three distinct regions known as the D, E and F regions. While the F region exists during both day and night, the D and E regions may vary in density. During the day, the D and E regions are more heavily ionized by solar radiation and so does the F layer, which develops an additional weaker region called the F1 region. So, the F region consists of the F1 and F2 regions. The F2 region is present in both day and night and is responsible for the refraction and reflection of radio waves.


Layers of the Ionosphere

The D layer is the lowest one and it´s the one radio waves reach when traveling up the atmosphere. It starts from about 50-80 km (31-50 miles). It´s present during the day when ultraviolet radiation from the sun interact with the molecules and atoms, stripping one electron off. After sunset, as solar radiation decreases, electrons recombine and this layer disappears. The ionization of the D region is due to a form of radiation known as Lyman-series radiation at a wavelength of 121.5 nanometers and ionizes nitric oxide gas present in the atmosphere.

The D layer attenuates radio signals passing through. The level of attenuation depends on the wavelength of radio signals. Lower frequencies are affected more than higher ones. This varies as the inverse square of the frequency, meaning that lower frequencies are prevented from traveling further, except at night when the D region dissipates.

The E region is the one that follows the D above the atmosphere. It´s found at an altitude of about 90-125 km (56-78 miles). Here, ions and electrons recombine very quickly. The levels of ionization drop fast after sunset, leaving a small amount of ionization present but this also disappears at night. The gas density at the E region is less than it is at the D region; therefore, when radio waves cause electrons to vibrate fewer collisions occur.

As the radio signal travels further up into the region, it encounters more electrons and the signal is refracted away from the higher dense electron region. The amount of refraction diminishes when the signal increases in frequency. The higher frequencies make it through the region and pass on to the next region.

The most important region for long distance high frequency communications is the F region. This region often splits into two distinct regions-the F1 and F2, during the day. Generally, the F1 region is found at about 300 km (190 miles) and the F2 region at about 400 km (250 miles). While the altitude of the regions in the ionosphere varies between regions, the F region varies the most and it´s affectedf by the variations of the sun, as well as the time of day and season of the year.

Maximum Usable Frequencies-MUF

Maximum Usable Frequencies-MUF
Maximum Usable Frequencies-MUF | Source

The Sun and the Ionosphere

The main cause of ionization of the ionosphere is the sun. The density of the ionosphere varies according to the amount of solar radiation. Solar flares, solar wind variability and geomagnetic storms affect the density of the ionosphere. Since the sun is the main cause of ionization, the night side of the earth and the poles are less ionized than those parts of the planet that point more directly to the sun.

Sunspots-dark areas on the surface of the sun, affect the ionosphere due that the areas that surround the spots emit larger amounts of ultraviolet radiation, which is the main cause of ionization. The quantity of spots on the sun vary according to an 11 year cycle. radio communications may be less during a solar minimum than during a solar maximum.


Sunspots and the Ionosphere

Sunspots and the Ionosphere
Sunspots and the Ionosphere | Source

Check your Knowledge of the Ionosphere!

view quiz statistics

Layers of the Ionosphere

D region 60 km (37 miles)-90 km (56 miles)

E region 95-150 km (59- 93 miles)

F1 region 150-210 km (93-130 miles)

F2 region over 210 km (130 miles)

The F2 region is the most used for radio communication due that it´s permanent day and night. The altitude at which it´s located allows for more ample communication and it reflects the higher frequencies.

Ground and Sky Waves

During the day, signals of medium wave frequency travel only as ground waves. As frequency increases, ionospheric attenuation decreases allowing signals to pass through the D region and on to the E region, where signals are reflected back to earth passing through the D region and landing at a great distance from the transmitter.

As signal frequency increases further, The E region electron density is not sufficient to refract signals and signals reach the F1 region where they are reflected back through the E and D region, eventually landing at an even greater distance fom the transmitter.

Higher signal frequencies will make it to the F2 region; due that this is the topmost ionospheric region. When those signals reflect off this layer back to earth, the distance traveled will be the greatest. The maximum skip distance that signals can travel when reflected off the E region is 2000 km (1243 miles) and when reflected off the F2 region that increases to about 4000 km (2485 miles).

The Ionosphere

Questions & Answers

    © 2018 Jose Juan Gutierrez

    Comments

      0 of 8192 characters used
      Post Comment

      No comments yet.

      working

      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, owlcation.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://owlcation.com/privacy-policy#gdpr

      Show Details
      Necessary
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Features
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Marketing
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Statistics
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)