That's according to a statement, external on Southern's website this morning. 

It says: "The strike will have a significant effect on Southern services on the whole of the day affected, with no service on many routes and only a limited service between approximately 07:30 BST and 18:00 BST on others, although we will extend the service hours if we are able."

A map showing the effect on a station by station basis is below.  

Image source, Southern

Scores of commuters have been using our hashtag this morning. 

Ben has emailed us this morning to express his concerns over the #Southernstrike, external, asking the government to 'take control'. 

Our reporter Mark Sanders travelled from Brighton to London Victoria on the Gatwick Express this morning, but he only endured a few minutes delay as they waited for a relief driver at Gatwick. 

Here's what James Abbott, the Editor of Modern Railways magazine, thinks about the strike action - and whether it will be resolved any time soon.

Here are some facts and figures about Southern.

RMT members have been protesting at Brighton station. #Southernstrike

A limited service is running today due to the #Southernstrike, external. But how has it affected your journey? 

You can get involved by tweeting, external us using #Southernstrike, external, emailing us or sending us a message on Facebook, external.

Aimee seems to be enjoying her trip this morning...

Southern, external has produced this map for commuters.

Cllr Peter Chowney, the leader of Hastings Borough Council, has this morning demanded action from the management of Southern to end the bitter dispute with its conductors.

He said “Today local rail customers have suffered a third strike day, with no Southern trains running to or from Hastings at all.

“This simply cannot continue indefinitely, and I therefore urge the management of Southern to do whatever is necessary to meet with the RMT, the conductors’ trades union, and resolve their differences.”

Claire Cottingham

You've been wishing commuters luck.

Our reporter Eleanor Roper is reporting from Brighton station this morning with the latest on the #Southernstrike, external. 

As disruption continues this morning due to industrial action, commuters at Brighton station have been expressing their frustration. 

Southern, external says passengers can get more information about how their journey will be affected today here, external. 

It includes details about train times, ticket acceptance and alternatives and compensation and refunds. 

Our reporter Mark Sanders is reporting from a train on the Brighton to London line.

Claire Cottingham

Here's Rachel Mackley with your forecast.

Here's what Charles Horton, Chief Executive of Govia Thameslink Railway, had to say about today's strike.

That's the message from Charles Horton, the Chief Executive of Govia Thameslink Railway, external, which runs Southern, external. 

Here's his letter to passengers.

You've been having your say this morning on Twitter, external using #Southernstrike. 

The BBC Sussex Breakfast Show's Neil Pringle will be speaking to Mick Cash from the RMT union, external and Tony Miles from Modern Railways Magazine at 08:08 BST.

Listen here.