The degree of subsequentiality of a subsequential filter

A space is called subsequential if it is a subspace of a sequential space. A free filter F on ω is called subsequential if the space ω ∪ { F } is subsequential. The purpose of this paper is to introduce the degree of subsequentiality of a subsequential filter in a similar way as it is done in the realm of sequential spaces. A method to produce subsequential filters with arbitrary subsequential degree is given.